Firstly, let the record reflect that
I called it.
Secondly, can we talk about how the MINIMUM base stat total on this thing is 694 (max 729), and its stats are pretty well optimised at that? They really didn't forget to make sure the stats made up for the lost item slot -- this thing basically functions as a mini-Primal. The fully powered forms will definitely be the ones used more often in competitive, partly because those stats are nuts (this thing will have physical bulk on par with Chansey's special bulk, but still has special bulk on par with Palkia aswell) and partly because their signature moves almost completely negate the benefits of Dynamaxing.
I don't see it pulling off a defensive set, because ubers will be chock full of steels and poison-types, and there is no obvious source of passive damage aside from burns (which I expect will be common in Ubers). I'm starting to think it almost doesn't matter that the old ubers aren't coming back, because the new ones would just obliterate most of them regardless. One possible liability on Zamazenta is that if Iron Head is replaced by its signature move, it won't have Iron Head to fish for flinches, and it won't appreciate Behemoth Bash's 8PP when it's trying to be bulky. It'll probably want to relearn Iron Head if it can, unless its movepool is really good.
Another thing is, Zamazenta is a fighting type, but what fighting attacks is it going to use? It's doubtful that it'll get Sacred Sword or Cross Chop, and it won't appreciate the defensive drops from Superpower or Close Combat. It will probably have to rely on low BP moves like Brick Break.