I got a very similar idea 2 weeks ago, it s funny :)
I would say that it's a bit hard to drive and aim at the zombies and not smashing them when I thought I would have. You could probably make it much better by finding a way to put much more zombies but lower their speed, lower our speed at first as well so it s easier to manouver and aim at zombies, as it should be the core loop, the satisfying part. Keep working on it :)