Decay should not harm Zombies who receive healing from poison. The debuff clearly says "Healing", not POISON.
What? NO! Reversing Regen like that is one of the great uses of Touch of Decay.
Poison HEALS the Zombie, it is hurting from that.
Does something absorb Fire? Touch of Decay, now fire damages it.
why do potions STILL hurt zombies? They have nothing to do with magical "Healing Magic" or "Holy Power".
I dunno you cure a walking corpse of being a zombie and see how healthy it is.