Buzzrocs were already playing baby Mewtwo for Mew-EX since Oceania, so now that Buzzwole is even more popular gives that baby Mewtwo more power. Zygarde is pretty underwhelming considering it 2HKOs stuff for 2 Energy in a format where Pokemon can do it for 1. It's especially underwhelming when you can attach the extra Energy and take prizes with Buzzwole. If Zygarde's 3rd attack was any more damage, it would a much better card. 110+Strong+Regirock+Choice Band=170. But maxxing out at 160 is pretty bad for the amount of Energy getting devoted to it. And already having Lycanroc which does do 110 for the same Energy, having a 2-Energy attack that OHKOs your target most of the time, being bulkier, having less retreat, Bloodthirsty Eyes, AND on top of everything else, the same weakness as Zygarde. I can't even say that Zygarde is useful early game because Buzzwole with Regirock+Strong KOs the little guys on the field. I'm going off topic, but I'll conclude that Zygarde doesn't do much, and essentially wastes deck space, baby Mewtwo(Mew is actually really good too) is a strong Mew-EX and mirror counter, and you essentially can't prevent Mew from attacking in the first place. If you could reliably do that, Zoroark wouldn't use it as a counter.