248 HP and 112 Defense EVs allow Mega Scizor to survive 2 Mega Lopunny Close Combats after Stealth Rock damage and 20 speed lets Mega Scizor to outspeed uninvested Heatran
Other viable spreads:
ㄴ Impish 248 HP / 124 Def / 136 Spe ㄴ Impish 248 HP / 252 Def / 8 SpD Ability in the tag: Technician / Light Metal (before Mega Evolving) From the pvp-mega-scizor tag
The given EV spread allows Mega Scizor to outspeeed Chien-Pao during Tailwind while maximizing its Attack, allocating the remaining EVs in HP.
Mega Scizor's Bullet Punch is one of the metagame's most reliable ways of dealing with Flutter Mane. Bug Bite is Mega Scizor's strongest STAB move, but Close Combat help Mega Scizor OHKO Heatran and Incineroar at +1.