Zombie is a status which turned any healing item/magic into damage, however damage will not be converted to HP. So, if you use Curaga with Yuna and heal about 78330, if you use it on the zombified character, the character will receive 78330 damage. The concept also work on Lancet, Drain, Cure/Cura/Curaga and all types of healing item such as potion or al bhed potion. If you use Full-Life/Life/Phoenix Down on the zombiefied character, they're death, if you cast Regen on the zombified character, then the character will have their HP reduce from time to time. Esuna or Remedy can't heal this status, you need Holy Water or save point, you can buy Holy Water at Calm Lands and Mount Gagazet. If you found your character to be zombied then remove the status immediately, this status is annoying. When you fight Yunalesca make sure you don't heal Zombie cause Mega-Death will kill all character that are not in zombie, cast Reflect on your party to avoid Yunalesca's Curaga.