It's a good concept, although the execution could have been a bit better. I found that it's way too easy to just keep spawning bombs on the player's head until they die, and then take a different route when you play as them.
A suggestion might be to not allow the player to place anything as the zombie master once the game is underway. That'll make the game far more tactical, since now you can't just win by taking a different route the original player did.