>>58150627
ZX was a wolf-like creature, because it hunts deer like Xerneas. This is probably where 10% Zygarde came from.
ZY was meant to be a humanoid form that uses anti-aircraft guns to shoot Yveltal out of the sky. Mega Zygarde seems to have been based around this scrapped idea, if this leak is true.

I also like how Mega Zygarde seems to have Rayquaza's markings on its body here? Like, even if Rayquaza is not in the game this definitely links them.