Zombie was a type of undead that make use of their own dead bodies. When LeChuck was killed in his ghost form, the remnants of the pirate's ghost beard was used to revive LeChuck in his old decaying body. During the Battle of Plunder Island, LeChuck has skeletons as part of his forces rather than ghosts. When LeChuck's body was obliterated except for his boots by his Voodoo Cannonball, LeChuck was revived into a flaming demon.
By the time, LeChuck reappeared after the curse of Monkey Island, LeChuck was able to switch between his ghost, zombie and demon pirate forms on his own.
LeChuck returned to his zombie form when he sought to perform a ritual with the Monkeys of Montevideo, however, he had some green glow coming off his beard and had the ability to push Guybrush back with his magic.
During Guybrush's death, the ghost of Guybrush was able to inhabit his dead body for a short period of time with the help of the Voodoo Lady's pendant. However, Guybrush is able to make the possession of his body permanent with the use of a special chewing gum.