The zombie villager profession overlays don't show on them but it said "added zombie villager profession overlays" in minecraft release changelogs 1.11.0 (Village & Pillage) but never did in any version after that so i'm going to say this is a bug that most certainly needs to be fixed! I'm sick of curing unwanted villagers and nitwits it's very annoying. So Mojang please fix this in your next release update.