People are acting like Zamazenta is fine because it can be checked. Yeah sure it can be checked, even without the nerf last gen it was possible to check Zamazenta-C. The problem with both Zamazenta (Zamazenta-C especially) is that they completely invalidates every physical attacking Pokemon the moment they enter the field. It doesn't even matter that the defense boost is only a one time thing, against offensive teams and especially HO it's all you need to completely K.O half or more of your opponents team. To me both Zamazenta to HO are what Annihilape is to Stall teams. Depending on the match up they are not going to seem broken but they make certain playstyle or Pokemon that are good otherwise completely useless.
People saying "cover legendary does not mean banworthy" are lying to themselves. The only time it happened in the past was because Kyurem and Kyurem-B had a terrible typing, no physically offensive ice stab, no DD, and a Stealth Rock weakness. With an Ice/Dragon typing, a slow Speed stat, only decent abilities and all the problems listed above of course they were fine. Necrozma is the only exception but it has only 600 BST, a terrible typing, weird stat distribution and only a decent movepool/Ability.
That's not the case for either Zamazenta. You are looking at what would be the 3rd fastest Pokemon on the metagame so revenge killing it with something faster is out of the question unless you are Dragapult or Speed boosting Iron Valiant. On top of that Zamazenta has an effective 130 Att stat and its movepool is decent enough to hit everything it wants to hit. But on top of being fast and hitting hard you are facing a Pokemon with 325 HP and 266 in both defenses (and I'm only talking about the basic Zamazenta, the bulk is even more ridiculous for the C form) uninvested and without adding the 1.5 boost from the ability.
Now add Tera on top of that and what can offense do without losing half of their team or even the game straight up ?
I don't know how anyone could think that a Pokemon like this is fine just because it doesn't do TOO well against particular playstyles.
At this point if you are going to allow stupid Pokemon just because they suck in Uber and/or can't hold an item you might as well make Arceus-bug OU.
I could see an argument being made for Darkrai, Deoxys-S or even Shaymin-S (it would still be stupid but hey some people think running Covert Cloak just for one mon is fine) but Zamazenta and Zamazenta-C are ridiculous.
In my opinion, unbanning Uber Pokemon should be something we do if they add something to the metagame, don't completely warp it around themselves and don't render certain playstyles or top tier Pokemon completely useless.
I would rather deal with Zygarde, Kyurem or Solgaleo than the Zamazenta duo.