I like the concept. It´s unique and the combination of two genres is nice, but the game is just too hard. A few more tips/opinions I have would be:
1. I don´t like that you aim with the arrow keys. I would make it so that you shoot the way you are facing.
2. You start with way too little bullets and a lot of zombies.
I love the art and the cutscene at the beginning is amazing.