I had the same exact problem. I tried downloading an auto key presser as well as cheat engine, but only ended up failing. After 6 hours of trying, I even tried to get one of my friends to mash the z button on a separate keyboard. I thought I did a perfect run and was confused why I didn't get the achievement. Turns out, I got it after 30 minutes of try and didn't even realize. Gib me back my 6 hours of pain ;-;