Yup, you can enslave zombie NPCs long as they're still a valid race, its an old PAHE exploit.  Just be careful if you use the following mod Necromancy -- Undead FX  The mod adds a skeleton inside the body of the NPC and this can bug your new slave (cause them to be stuck in a T pose because of conflicting animations)    An yeah, I sold Larina back to what's her name that sent you for the flute that Larina stole.  ?