Has anyone actually tested BA zoo,? it sounds terrible in theory with the fact that you need to play a sufficient amount of them to draw together that you wouldn't be able to play key zoo cards needed. Secondly a lot of synergy off of BA is the ability to mill them which also doesn't synergize well with a zoo deck unless you are playing a ton of BA. Lastly you can't make a board of BA and zoo at the same time. That deck idea really seemed like bait to get people to make poor choices/
As for Metalfoes Zoo, the higher the concentration of pendulum cards the greater the consistency and synergy. There was a list going around from a player who tied a 1k cash tournament and his deck was pretty poorly constructed with 13 MF monsters and 47 cards in main deck, i know some people that tested it at a pretty soft locals and bricked super hard.
In the new format much like the last we will see Pure Zoo, True Draco Zoo, and Kaiju Zoo.
Even in this classification i think that true draco engines will now become larger to the extent that TDZ (true draco zoo) is now more like True Dracos with Zoo. Most people have realized that the small ( lvl 5-6) True Draco provide more consistency and utility than just playing 2-3 master peace. a lot of lists i have seen use 2-3 dinomight knight, 2 master peace, and 1 of Ignis or majestys maiden.
I think the real question is what are people who play pure and kaiju zoo doing to fill up their monster slots as i have a lot of experience with not drawing any monsters/searchers at all with 10-16 monster lists.