Having already played this once for GDM, I was expecting to breeze through this game and rate it out of politeness, but it was honestly utterly brutal. I think it literally took me hours because there were so many attempts that ended in failure. It felt like no matter what I tried, no matter what items I got, the game would screw me over one way or another. Despite this, I still persevered because I simply didn't believe it was impossible, and eventually I got lucky enough to clutch a win (and I've got the screenshot to prove it). I suppose my feelings of determination in the face of hopelessness and overwhelming odds are apropos for the zombie apocalypse setting, but I'd imagine some people might not have that level of patience (especially given how many commenters said they didn't know what they were doing).
Overall, while most things about the game were well-done, my main problem was that victory seemed to be based more on luck than skill. I'm not entirely sure how I'd "fix" that, but I think having the game's overall RNG be slightly more in the player's favor would help mitigate the issue. Also, I don't know if you made it so that stronger zombies more frequently get you better items when you beat them, but I think doing something like that would make it more worth going after them, so that the reward matches the risk. As is, I'd often ignore things because I didn't think they'd be worth the trouble. 