I am not a Axis & Allies player, but I play a lot with Conquest of Nerath. I like this zombie version.
I believe that can be improved.
These are my house rules
Deadnapper convoys revised . Add to existing rule: Shore zombie bombardment In a amphibious assault your transport can fire once against zombies: score an hit . Its attack value is (3).

Strong Neutrals: When a zombie card create an outbreak in a neutral territory add 6 zombie in 2 IPC territories (Turkey and Spain )and 3 in the other (1 IPC value) territories -(“call us neutral not zombies !”)

Zombie apocalypse revised (not so easy allies victory ).The side that controlls the greates number of zombie-free territories wins. In case of tie who controll the greatest IPC value of zombie-free territories win.
Different set up every game . Starting purchase : place everywhere pieces on the game board in territories/sea zones (example I have not text this )
add 4 IPC Russia
add 3 IPC Germany
and 6 IPC UK
add 8 IPC Japan. /
add - IPC to US
I try also to use Nerath deployment rules:

Moving New Pieces: Once you have placed your new pieces,they can immediately move from the space where you placed them to any friendly space they can reach with their Move. Doing this lets you position new troops to defend against enemy counterattack. New Warships carrying new land pieces can immediately move, carrying those pieces, and unload them in a friendly land space. However, you cannot move an existing Warship that you placed new land pieces on. Enemy Sea Spaces: You cannot place your new Warships and Storm Elementals in enemy sea spaces, even though they can move after you place them

If you have 14/16 Ipc to spent you can immediately reinforce a new conquered territory by boat or make a land invasion more easy.
It seems that this variant helps more the Allies
What you think about gameplay(forget realism,you are playing with zombie ;-) ) ?