Let's for one second remember that these creatures are fictional...as in they don't exist. There will ALWAYS be a chance for mixing things up, you just need a writer willing to cut through the cliches and design say... a vicious zombie virus which deforms the vampire virus, causing massive changes in physical and mental form/abilities. As for werewolf zombies, the werewolf is supposed to be human most of the time anyway.
OT I think a Vampire Werewolf would be cool, although the one in underworld sucked. Adding zombie to anything would just make it dumb and slow... so no lol.