If that were the case, in their wolf form, they would be pretty much invincible to the zombies unless they got pinned down and dragged into a hoard of zombies.
But in human form, they could be Zombified, and would likely lose their werewolfness because that is a living disease.

In such a case, if the humans were smart enough. They could possibly survive, perhaps in water or something on a boat, and only going to shore in wolf form.