Very interesting!
I really like your creative interpretation of the theme (although I admit I did not read the description of the game and got very confused when I changed into the zombie controller xD).
Presentation was very good. Art and Sound design fit together well. I appreciated the variety of weapons too.
For improvements, there's the diagonal movement that others have mentioned. I'd also recommend adding a Zombie SFX or bigger flashing icon pointing to the zombie when you change between Gorilla/zombie mode (just to make it crystal clear).
Overall, very strong submission. Well done!