So I tried some new things. I haven't done any damage calculations yet, so all of the EVs are still 252/252. I went with the standard: 2 Physical Attackers, 2 Special Attackers, 1 Physical Wall and 1 Special Wall.
Mega Flygon (Zygarde) @ Lum Berry
Ability: Aura Break
EVs: 252 Atk / 4 SpD / 252...