Got some noms for the VR:
B -> B+ / A-
Being able to run Mold Breaker is huge atm when we have stuff like Multiscale and Unaware plaguing the metagame. Mega Gyarados is by far the best user imo since it can fit on quite a few playstyles ranging from rain offense to even some balance teams. Having access to moves such as Taunt and having Intimidate as a pre-mega ability also means it can provide some team support on its own before it attemps to sweep. Its weak to priority, but pair it with Dazzling / Queenly Majesty and other stuff to buff it up such as Adaptability and Simple and we have a deadly sweeper on our hands.
B+ -> A-
A staple on a majority of HOs, Shuckle can provide both Contrary and Sturdy which can be really useful for a lot of teams. Being able to setup both Webs and Stealth Rock is also really good for it since it can act as a great standalone mon as well, and having access to other useful abilities like Multiscale and Magic Guard makes it even more annoying to deal with. Probably the best suicide lead entry hazard setter availible.
C+ -> B
Poison Heal is one of the best donor abilities imo and Gliscor is the most viable donor. Not only can it give off such an incredible ability that pairs well with other great abilities such as Guts and Marvel Scale, but Gliscor itself is also a rather viable poke on its own, potentially acting as a entry hazard setter / remover, setup sweeper, or general anti-stall mon thanks to moves such as Taunt + Toxic. Can fit on anything from offense to full on stall and is generally one of the best donors atm, which is why I believe a rise to at least B is warranted.
B -> C+
I get Magnet Pull is a nice ability and all, but I don't think it propels Magenzone to B. Steels are common atm with stuff like Excadrill, Celesteela, and Magearna, but most of the aformentioned steels either outspeed potential Zone partners thanks to weather or can beat them out when paired with abilites such as Multiscale or even Volt Asborb (in Celesteela's case). Even for Electric Terrain teams there are much better options such as Xurkitree and Thundurus to aid in wallbreaking. I just don't see the niche in Zone even with it's other abillities since they don't offer too much compared to the other mons it's ranked with.
UR -> B-
A cool setup sweeper to break stall thanks to it passing Moxie and having access to Power Trip. Works well when combined with Simple + Beast Boost + Soul-Heart combination. Unfortunately do not have replays showing it off but trust me when I say it works.
UR -> C
Cloud Nine is like almost a must on a majority of non-weather HOs if they don't want to get dicked on by opposing weather. Drampa is a cool donor since it can Defog away hazards and actually hit really hard with it's stabs (also Prankster Nature Power shenanigans are also annoying to deal with). It's definetely more of a filler mon that just provides a useful abiltiy which is why C is a good start for it imo.
UR -> C
Before claiming it as a meme, Eevee can work really well as not only does it pass Adaptability, but also can be quite a potent setup sweeper on its own with Extreme Evoboost + Simple + Anti-Priority. Even though it has piss poor offensive stats, it can actually still break teams after an aduquate amount of boosts, with Stored Power allowing it to break through stall teams as well.
Replay of it in action: https://replay.pokemonshowdown.com/rom-gen7sharedpower-197676
I would nom some Harvest stuff but I would rather wait a bit on that to really see if its just a gimmick. Great job with inital rankigns so far!

Being able to run Mold Breaker is huge atm when we have stuff like Multiscale and Unaware plaguing the metagame. Mega Gyarados is by far the best user imo since it can fit on quite a few playstyles ranging from rain offense to even some balance teams. Having access to moves such as Taunt and having Intimidate as a pre-mega ability also means it can provide some team support on its own before it attemps to sweep. Its weak to priority, but pair it with Dazzling / Queenly Majesty and other stuff to buff it up such as Adaptability and Simple and we have a deadly sweeper on our hands.

A staple on a majority of HOs, Shuckle can provide both Contrary and Sturdy which can be really useful for a lot of teams. Being able to setup both Webs and Stealth Rock is also really good for it since it can act as a great standalone mon as well, and having access to other useful abilities like Multiscale and Magic Guard makes it even more annoying to deal with. Probably the best suicide lead entry hazard setter availible.

Poison Heal is one of the best donor abilities imo and Gliscor is the most viable donor. Not only can it give off such an incredible ability that pairs well with other great abilities such as Guts and Marvel Scale, but Gliscor itself is also a rather viable poke on its own, potentially acting as a entry hazard setter / remover, setup sweeper, or general anti-stall mon thanks to moves such as Taunt + Toxic. Can fit on anything from offense to full on stall and is generally one of the best donors atm, which is why I believe a rise to at least B is warranted.

I get Magnet Pull is a nice ability and all, but I don't think it propels Magenzone to B. Steels are common atm with stuff like Excadrill, Celesteela, and Magearna, but most of the aformentioned steels either outspeed potential Zone partners thanks to weather or can beat them out when paired with abilites such as Multiscale or even Volt Asborb (in Celesteela's case). Even for Electric Terrain teams there are much better options such as Xurkitree and Thundurus to aid in wallbreaking. I just don't see the niche in Zone even with it's other abillities since they don't offer too much compared to the other mons it's ranked with.

A cool setup sweeper to break stall thanks to it passing Moxie and having access to Power Trip. Works well when combined with Simple + Beast Boost + Soul-Heart combination. Unfortunately do not have replays showing it off but trust me when I say it works.

Cloud Nine is like almost a must on a majority of non-weather HOs if they don't want to get dicked on by opposing weather. Drampa is a cool donor since it can Defog away hazards and actually hit really hard with it's stabs (also Prankster Nature Power shenanigans are also annoying to deal with). It's definetely more of a filler mon that just provides a useful abiltiy which is why C is a good start for it imo.

Before claiming it as a meme, Eevee can work really well as not only does it pass Adaptability, but also can be quite a potent setup sweeper on its own with Extreme Evoboost + Simple + Anti-Priority. Even though it has piss poor offensive stats, it can actually still break teams after an aduquate amount of boosts, with Stored Power allowing it to break through stall teams as well.
Replay of it in action: https://replay.pokemonshowdown.com/rom-gen7sharedpower-197676
I would nom some Harvest stuff but I would rather wait a bit on that to really see if its just a gimmick. Great job with inital rankigns so far!