S Rank
Gyarados-Mega--Not as cut and dry as you might think. Life orb never kills Gyara-mega turn one thanks to intimidate, and a decently invested adamant mega gyara can ohko no bulk with eq (116+ Atk Mold Breaker Gyarados-Mega Earthquake vs. 0 HP / 0 Def Zeraora: 318-376 (100.3 - 118.6%) -- guaranteed OHKO). Even Electrium Zera doesn't always pick the W (tho the chances are low) (-1 252 Atk Zeraora Gigavolt Havoc (180 BP) vs. 0 HP / 0 Def Gyarados-Mega: 326-386 (98.4 - 116.6%) -- 87.5% chance to OHKO). Thankfully, there exists a nice little move called Bulk Up. Only max speed jolly gyara can outspeed a Naive Zera at +1, so if you fake out+bulk up+life orb plasma/gigavolt/pummeling, you're getting the W. On the special side of things, Z-thunder will probably pick up the ko, unless max spdef becomes a thing, z-focus blast and special life orb/specs will not pick up the ko, and thus you will need to worry about the aforementioned 116+ attack eq. Gyarados can only win if the opposing zera is z focus blast/life orb/specs zera, and it has enough attack to ohko with eq, or if it is fully offensive gyarawith 252+ jolly and they bulk up after fake out, predicting bulky gyara, in which case gyara can outspeed and most likely pick up a ko with 252 jolly eq.
Mostly Zera W
Tapu Koko--A fully electric move koko loses to every set, but if you run ID roost koko, you might be able to stall the zeraora to death, especially if it's a life orb physical set (Pp stall koko, what a novelty). Specs just full on loses, outsped and 2hkoed by zera. Not an unwinnable matchup for koko, and if it remains in 1v1 by the time Zera is released, I fully expect the koko meta to shift to sets that 100% beat zera, in one way or another.
Zera W if offensive, Zera L if ID Roost
Edit 7/1/18 Koko whats that lmao
A+ Rank
Charizard-Mega-X--Probably a char x win. I can imagine some shenanigans with fightinium on non-bulky char and misplays, but for the most part, a char x win.
Zera L
Dragonite--Zera picks up the kill if its against 0 HP/0 spdef dnite with fake out into hp ice, max special attack and life orb. Can also win against with fake out into bulk up into z-plasma against flyinium. Otherwise, beaten by eq or dragonium, I can't imagine the dnite meta won't shift to include the minuscule amount of evs needed to always live through max spa Zeraora.
Pretty much Zera L
Magearna--Probably a mag W. Only chance Zera has is if it runs sub against specs mag and gets good rolls (-2 252+ SpA Choice Specs Magearna Fleur Cannon vs. 0 HP / 0 SpD Zeraora: 211-249 (66.5 - 78.5%) -- guaranteed 2HKO, so in Zeraora's favor).
Mostly Zera L
Metagross-Mega--Another probably meta W. Bulky meta is the meta, and zera doesn't stand a chance with bulky meta (except Z-thunder zera, which can occasionally 2hko a spdef metagross with z thunder into regular thunder (good luck)). Zera can win if A) Meta runs no bulk and B) it gets the 31% low roll with jolly eq (or if they don't run EQ on their non-bulk metagross).
Mostly Zera L
Mimikyu--Mimikyium ohkoes 80% of the time. (adamant 100%), z-plasma will ohko unless 252/8 def, but that doesn't matter because offensive mimi always carries sneak. Again, Zera could win with sub, if Mimi gets low rolls. Zera probably beats cursekyu, as even a non-life orb plasma fist can 2hko a 252 hp mimikyu, but will o/charm could cause some issues.
Zera loses most of the time to offensive, wins most of the time with curse, mileage may vary with substitute.
A Rank
Charizard-Mega-Y--No lol,
Zera W
Landorus-Therian-Life orb fake out into hp ice always wins vs if max Special attack (unless spdef landoT), no special attack hp ice into fake life orb is a roll until 216 HP lando, at which point it never kills, never guaranteed at any point.
50/50
Snorlax--Even tho Plasma fist's "turn normal into electric" is a thing, yawnlax is a whore and can hax you if bad luck. life orb 252 cc never kills 252 hp lax, and yawnlax (should) always run protect, so the extra fake out damage won't help. With z-close combat, its a 50/50 if they protect or not, but you can easily beat the stallax curse set regardless, as life orb cc does more than 50 even with 252/252 hp def lax, where they will be forced to rest before they can not be 4hkoed by cc. With special fightinium, Zera probably won't win.
Edit 7/1/18: Didn't know that yawn was affected, but lax still beats any special set.
65/35 Zera W
Tapu Lele--Bulky Lele wins, specs no bulk loses, scarf no bulk is a 50/50 at best (252+ SpA Tapu Lele Psychic vs. 0 HP / 0 SpD Zeraora in Psychic Terrain: 291-343 (91.7 - 108.2%) -- 50% chance to OHKO).
Zera win in low tier, Zera L in high tier
Zygarde-Complete--
Zera L (sigh, you can technically sometimes win with life orb max special attack fake out into ice with a no bulk zygarde. No bulk zygarde isn't a thing)
A- Rank
Aegislash--
Mostly Zera L vs Ghostium Aegi, Mileage may vary with sub Zera
Genesect--Easy 2hko/ohko with Zera's electric moves, unfortunately gene doesn't get the spa boost if Hasty, so specs bug buzz doesn't ohko, except with a 20% roll with modest.
Zera W.
Lopunny-Mega--
Zera outspeeds and bops with fake out into Z or life orb fighting move, Zera W
Magnezone--
Zera W (Volt Absorb)
Mawile-Mega--
Zera L except special z-thunder against speedy mawile (except speedy Hyper Cutter Mawile, which loses to bulk up into z-plasma, if u get the 50/50 right on sucker)
Porygon-Z--
Zera W against all except scarf timid
Slowbro-Mega--Very interesting here. 252 Hp/252 Spdef slowbro
Can win against life orb physical zeraora, and consistently too, and you can sometimes beat Z-plasma with 252 Hp/252 Spdef if you slack off when it z moves (you will live physical z if they don't get a high roll) (252 Hp/252 Def is guaranteed to live. After that, you can iron defense and slack off till you can safely scald and take the W. However, a few issues; Zera can learn taunt, which would force you to stay non-mega and therefore z-plasma and life orb plasma will ohko and 2hko, respectively. And special wise, you really only have a chance with z-focus blast, where with 252hp/252 spdef you can sometimes live fake out+tbolt+tbolt after a turn 2 cm, will always live with turn 2 amnesia. Otherwise, life orb tbolt 2HKOes always and z-thunder ohkoes, calm mind could pose some issues as well.
Surprisingly closer to a 50/50, leaning towards Zera W regardless
Venusaur-Mega--
Zera L
B+ Rank
Aggron-Mega--Pretty cut and dry; Aggron wins w/ eq/metal burst against physical, special Zera can sometimes live non-252 adamant eq and follow up with a special z move, but you'd have to be wary of metal burst.
60/40 Zera L
Blaziken--252+ Atk Blaziken-Mega Flare Blitz vs. 0 HP / 0 Def Zeraora: 319-376 (100.6 - 118.6%) -- guaranteed OHKO.
Zera will lose unless bulk up/sub (even then, blaziken could SD and take the W)
Donphan--Zera will lose except with life orb fake out into grass knot. Need 208 spa investment to guarantee, you will beat 0 hp donphan with 0 spa grass knot after fake out.
Mostly Zera L
Gardevoir-Mega--
Zera L. Gardevoir can stay non mega and trace volt absorb, resisting 4x cc.
Golem--Fake out into life orb grass knot/focus blast, regular focus/z-focus blast all kill. However, life orb close combat, z close combat, and regular close combat w/ z electric fail to pick up the W with high hp golem, which people run to get better damage with counter. Overall, special wins always, physical sometimes can,
50/50
Greninja--Scarf can give some issue, but even modest scarf hydro cannon can't ohko 100%. Scarf hp ground seems solid, until one realizes and z-cc or z-focus move kos after fake out when it is ground type. Gren can win if it is scarf and either gets the good roll w/cannon or they are electrium Zera (life orb cc can still ko after life orb fake out).
Inconsistent Zera W (yayyy, more scarf gren on ladder,,,,,

)
Jumpluff--Life orb Zera always wins, Electrium wins after fake out if they get the protect 50/50 right, physical fightinium loses, its a roll with fake out into ice with special fightinium.
60/40 Zera W
Naganadel--get oofed,
Zera L. Don't even need to risk draco, sludge will kill.
Pinsir-Mega--This ain't gen 6, protect pinsir ain't a thing,
Zera W (eq pinsir can beat fightinium pinsir exactly 6.3% of the time w/ jolly)
Primarina--LMAO
Zera W
Tapu Fini--LMAO
Zera W
B Rank
Altaria-Mega--Most definitely a
Zera L. Life orb can sometimes beat non-bulky altaria, but like non-bulky zygarde, that doesn't exist
Chansey--Surprisingly, Z-fightinium Zera is not as surefire as one may think, assuming no crits. Chansey softboils on the z, and then it can't do enough to pick up a kill before you run out of close combats, then chansey toxic stalls to victory. Life orb physical is another story, you will eventually win with cc after cc if they decide to softboil stall. Bulk up zera will win, as well. Special sets, as per usual with chansey, have no chance. Overall, I would say a
60/40 Zera L
Ferrothorn--Special will win if you're lucky with focus blast, with z fightinium you need to predict protects and get lucky with focus blast, z-plasma has no chance unless bulk up.
70/30 Zera L
Garchomp--Special life orb can win with fake out into hidden power ice against non-scarf garchomp, with hp it becomes a roll but not impossible. Only scarfchomp wins 100% against max special life orb zera. However, garchomp beats every other set.
70/30 Zera L
Heatran--Earth power kills zera at -1 spdef, so ccing turn one/after fake out is suicide, but there are easy ways to get around this, such as using a z move to get them in range of cc, or using focus blast. Heatran is much better suited for life orb zera, where it can sufficiently ev to live a life orb cc or focus blast and get a guaranteed ko after life orb recoil. Still, matchup not entire in heatran's favor,
65/35 Zera W
Heracross-Mega-- Zera can only win if it gets high rolls against a no hp hera, which is basically not run.
Zera L
Kartana--Interestingly, Zera wins with all of its sets except z-plasma fists w/o bulk up. Z-focus and z-cc do enough, z-thunder ohkoes oc.
Zera W
Meloetta--Plasma fists turn hyper beam into health, so it comes down to specs psychic, which has a 44% chance to ohko. Zera also naturally outspeeds scarf modest, so they will be forced to psychic unless scarf timid.
65/35 Zera W
Mew--80 modest mew can ohko no bulk zera with genesis 100%, for Zera its a roll to kill no bulk mew with fake out into z. No bulk mew isn't a set. Only exasperated by stall mew, which Zera only can beat with taunt.
Mostly Zera L
Necrozma--Like with mew, Necrozma is going to ohko easily, whether it be with specs or cm w/ moonlight. And like with Mew, Zera has a roll to kill no bulk necrozma, but its not guaranteed, and like Mew, no bulk necrozma isn't a set.
Zera L, mileage may vary with sub
Sableye-Mega--
Zera L, too much bulk for zera to overcome, no scrappy to save it.
Sawk--Take that W, Zera. You're outspeeding and killing after fake out all but scarf jolly, who only kills 6.3% of the time with eq.
Zera W
Tyranitar-Mega--As per usual, fighting moves neuter ttar, made worse by Zeraora's access to bulk up and still outspeeding max speed ttar at +1. ttar might have a chance with z-thunder and life orb focus blast,
for the most part Zera W, tho keep in mind max def counter ttar
B- Rank
Blastoise-Mega--Lol
Zera W, tho can sometimes win rolls with life orb tbolt and ohko with hydro
Blissey-- Because Blissey doesn't have the same physical bulk, physical zera always wins, even after a z-charm. Special might have a chance with calm mind at +3.
50/50
Buzzwole-Swoleman beats every set except sometimes z-thunder, who can 2hko av swole 252 hp 0 spd and even after leech life recovery. Otherwise, swole ohkoes with eq or a z move.
Mostly Zera L
Celesteela--Ded.
Zera W, tho be wary of protect if you run thunder, as you can get real unlucky real quick
Crustle--Loses to bulk up and z-thunder crustle, beats every other set with z-rock wrecker. Keep in mind you don't outspeed after a shell smash, but you don't need the attack, z-rock ohkoes at +0.
75/25 Zera L, mileage may vary with sub
Diancie-Mega--Diancie beats life orb and z-focus, loses to electrium-z and z-cc.
55/45 Zera L
Durant--The bug loses to every special set and z-plasma, beats everything else. Given into account hustle,
60/40 Zera W
Gengar-Mega--Ohkoed by Electrium, 2hkoed by everything else. Really just depends if hypnosis hits, bc then Gengar ohkoes with hex.
75/25 Zera W
Hoopa-Unbound--Loses to physical zera, beats special zera with either z or band/specs.
50/50 Zera W
Kommo-o--Nah. Kommo-o too bulky.
Zera L
Swampert-Mega--Life Orb fake out into Grass knot pretty much wins, without a life orb things get iffy.
80/20 Zera L
Togekiss--Death to serene grace,
Zera W
Whimsicott--
Zera L, unless taunt into 252 life orb hp ice, in which case the whims needs spa investment to kill with moonblast before Hp ice kills
C+ Rank
Archeops--Beats all but scarf, which beats it first 55% of the time.
85/15 Zera W
Avalugg--252+ Atk Avalugg Avalanche vs. 0 HP / 0 Def Zeraora: 255-300 (80.4 - 94.6%) -- guaranteed 2HKO, 252+ Atk Avalugg Earthquake vs. 0 HP / 0 Def Zeraora: 282-334 (88.9 - 105.3%) -- 31.3% chance to OHKO. 1/3 chance to ohko with eq, if you can even live after fake out, you will only consistently beat life orb.
75/25 Zera W
Camerupt-Mega--
Zera L
Carracosta--
Zera W
Excadrill--Zera won't beat scarf, but every other set gets bopped by fighting moves, even from the electrium sets, for the most part.
70/30 Zera W
Gallade-Mega--Only electrium z wins consistently.
60/40 Zera L
Latios--Nope.
Zera L
Lucario-Mega--
Zera W, we dem frailbois
Marowak-Alola--
omae wa mou shindieru
Medicham-Mega--You will lose against all except fightinium.
70/30 Zera W
Pheromosa--most phero rn run modest/adamant, that might change if zera becomes important enough. A stab z move from phero will kill, but fake out into anything will kill from zera.
50/50 Zera W
Porygon2--Only Life Orb physical can win, everything else is outstalled. Taunt could lead to a W, but I tri attack does too much, especially after the spdef drop of cc (tri attack will not be affected by plasma fists if p2 traces volt absorb).
70/30 Zera L
Scizor-Mega--Z-thunder kills a no bulk scizor, and mostly kills after fake out with a 252 hp scizor, any spdef and it becomes unlikely. Special life orb can 2hko 252 hp as well. Also, bug bite 2hkoes unboosted.
65/35 Zera W
Tapu Bulu--No lol.
Zera L
Terrakion--Scarf can't kill,z/Lo fighting moves ohko, z electric almost always ohkoes after fake out.
Mostly Zera W
Umbreon--Taunt and bulk up Zera shut it down, besides that Special sets basically lose.
60/40 Zera W
Victini--Scarf v-create ohkoes, fake out into z-plasma has a low chance to kill, leaving you susceptible to band vcreate.
90/10 Zera L, mileage may vary with sub
Volcarona--Electrium and physical LO wins, everything else loses, I'd say
60/40 Zera W
C Rank
Blacephalon--Scarf blace wins, non scarf is bopped by electrium and life orb plasma.
55/45 Zera W
Deoxys-S--
Zera L, beaten by both stall and specs
Entei--More in Entei's favor; bulky can usually live a fake out into z and bop with a fire move into espeed.
60/40 Zera L
Garchomp-Mega--Nah son. Too bulky.
Zera L (zera can kill uninvested 6.3% of the time)
Haxorus--Only special fightinium z can sometimes kill this after fake out, everything else fails to and dies to eq.
Mostly Zera L
Hydreigon--Bopped by LO and z-fightinium, scarf only has a 20% chance to kill with draco. z-plasma sets can sometimes pick up a kill with fake out into cc; z-thunder cannot.
80/20 Zera W
Infernape--Loses to every set.
Zera W
Keldeo--
Zera W
Landorus--Life Orb fake out into hp ice will kill, as will special zera fake out in hp ice, everything else won't. Bulky Lando-I isn't run, so
60/40 Zera W
Latias-Mega--
Zera L
Nihilego--Physical sets win, special sets lose.
65/35 Zera W
Ninetales-Alola--Physical sets win, special sets lose, except for fake out into z-thunder.
70/30 Zera W
Pidgeot-Mega--
Zera W
Relicanth--
Zera W
Thundurus-Therian--
Zera W (HP Ice)
C- Rank
Hitmonlee--Respect endure liechi berry, and you won't lose.
Manectric-Mega--
Zera W
Pyukumuku--
Zera W, be wary of max hp max def counter
Quagsire--you lose unless grass knot,
mostly Zera L
Rhyperior--Only beats physical, loses to special life orb and special fightinium,
60/40
Serperior--Uninvested, serperior can't tank any two fighting/ice hits with z and life orb respectively, but idk how serp should be eved, and therefore don't know if the defenses need to tank the moves is viable.
Unclear
Salazzle--Electrium and life orb wins 100%, everything else has a good roll to win.
Mostly Zera W
Skarmory--
Zera W
Stakataka--Mostly beaten by Life orb and fightinium, electrium is a roll with special after fake out.
70/30 Zera W
Suicune--
Zera W
D Rank
Abomasnow-Mega--Mostly beaten by Life orb and fightinium, electrium cc/focus never kills.
65/35 Zera W
Alakazam-Mega--One of the few things that can outspeed, it still gets bopped by electrium and physical life orb.
60/40 Zera W
Aron--
Zera W (fake out)
Azumarill--
Zera W
Barbaracle--
Zera W
Clefable--Electrium can win consistently, as well as taunt.
60/40 Zera W
Dusclops--Taunt shuts it down, otherwise a loss for Zera.
Mostly Zera L
Sceptile--252 SpA Sceptile-Mega Leaf Storm vs. 0 HP / 0- SpD Zeraora: 309-364 (97.4 - 114.8%) -- 81.3% chance to OHKO.
81.3/19.7 Zera L
Slaking--Fake out, but also 7% scarf usage.
Mostly Zera W
Smeargle--
Zera W
Stunfisk--woag.
Zera L
Type: Null--Unless taunt, there might be some issues.
Mostly Zera L
Vivillon--
Zera W
Volcanion--
Zera W