Against Zhu you want lot of undead attacks because all his pets are humanoid. One of them uses mainly critter attack though so you don't neseccarily want all of the pets to be undead, there are plenty of non-undead pets with undead attacks too. Although its doable with undead also, I think I used something like ghostly skull, blighthawk, and Mr. Grubbs in beating him. Start with ghostly skull, use shadow slash until your skull is almost dead, then do unholy ascension, and on the bonus undead turn ghostly bite, switch to Grubbs, acidic goo, consume, leap, consume, just use this rotation until Grubbs dies, which doesn't happen too fast since consume is strong against humanoids so makes Grubbs to heal like crazy, then if there is still something left from their side when Grubbs dies, blighthawk with infected talons, ghostly bite, and lift-off should be able to finish it off. Oh and about any maggot pet works in place of Grubbs since I think they have the same move set, I just like Grubbs because of his huge health pool.