Will a zombie go away if I go into peaceful mode in the nether?

I have a zombie in my villager trading hall to zombify villagers and I wanna build a ghast farm in the nether, however bcuz the nether has a bunch of dangerous mobs I wanna turn it to peaceful whilst building (yes I’m a scaredy cat), I have the zombie name tagged is there anyway to make it so he won’t dissapear? Or will he respawn when I put it back to normal mode?