As far as I'm aware, there isn't a mod/hack for Nazi Zombies, as if there was one, it would require up to 5 different save datas (Nacht Der Untoten, Shi No Numa, Zombie Verruckt, Der Riese, Online, and possibly campaign). Also, it would be impossible to hack it even if there was a way, because Treyarch encypts their savedata into a code that no one knows except from the workers of Treyarch. I've tried an online encypter/decrypter, and the closest thing I got to hacking was using Binary (which is MILES off the encrypted savedata). So there won't be any hacks for WaW for along time. Sorry buddy.