Hypersmurf said:"The rules don't cater for the Notch Theory of Creature Speed" and "The rules are ambiguous" aren't logically equivalent, though.
Zombies are creatures, and the effects of Haste on creatures are unambiguously stated.
-Hyp.
Hyp is correct, its hard to argue otherwise. It clearly states what haste does. Raw he's correct. whether or not it SHOULD work that way is whats up for debate.
There are no rules for spells supressing natural abilities, so your just gonna have to house rule what works for you.