I uninstalled my old zbrush thinking that was the problem but no. I restarted, same thing. Everytime I try it gets right up to where it says installing and the last time I just left it for an hour and it still got no further. I even tried installing it on another drive. Nope. I even redownloaded it with my virus scan turned off. Nope, same thing.
Sorry you’re having some trouble!
To clarify, you want to disable AV for the entire installation process, not just the download. It is a common cause of issues.
Otherwise, if this doesn’t address your issue, I’d advise you to make a support ticket. They are much better equipped to troubleshoot installation issues there than we are here.