In my opinion, a zombie is not difficult to draw than it would be more absurd to move in order then to be interesting :)

По моему мнению, зомби нарисовать не сложно, чем нелепее он будет двигаться тем будет интереснее :)

I really like the stair case. Well done.

The perspective of the piece is interesting, but I can't say I understand it.
On the right side of the image it looks like there's the outside of a building on the bottom, then on top of that there's a room in the building from a bird's eye view with a gun in it, then the guy standing... on the room?
Is this going to be a paper craft?

Anywho, I'd recommend eliminating all the jaggies on the two characters. For example, both of the zombie's arms and the leg on (our) left side.