Thanks for the review. During zombie mode you don't need a mouse so you can simply use your hand on the arrow keys instead.
What do you mean by stopping you completely?
Ah, I thought you could shoot if you had a zombie with a gun and you would need the mouse for that. I'd still prefer not to change my hands that much between the modes. Maybe clicking to take control of a zombie or scrolling through the different zombies could make for a good alternative control scheme
By stopping completely I mean that if you press and hold both A and S (for example), your character doesn't move.