At the beginning of combat on your turn, you may integrate another creature you control. If you don't, tap Xavvac, Corrupter Core.
Permanents you control with cards integrated onto them have lifelink and deathtouch.

Whenever you cast a spell that targets Zenith Marshal, create a 1/1 white Human creature token. If Zenith Marshal is attacking, that token enters tapped and attacking.
As long as Zenith Marshal is attacking, other creatures you control get +1/+0.

Flying
Amity — Whenever you attack with Zipping Lightningbug and exactly one other creature, target creature you don't control gets -2/-0 until end of turn.

Flash
{2}{B}, Discard Zyxthax Apex: Each opponent loses 3 life and you gain 3 life.
{6}{B}{B}: Return Zyxthax Apex from your graveyard to the battlefield tapped with a finality counter on it.