Turns out you still need to put the correct files into the correct folders in your file system here in 2022.
An audio plugin to be installed and available to your installed audio apps needs to be installed per their instructions. There may be installer and uninstaller scripts provided. Try that first (because least effort).
Installing manually...
Yeah, you absolutely need to unzip it!
You'd need to put the plugin in the correct folder. (.vst, .vst3, etc) If it was a more complex install with application support or library files, you'd have to learn that and put those parts in the right places. (That installer script is looking more attractive now, yes?)
If you did a partial or screwed up install... Now an installer script might run into unexpected crap and fail. You'll have to hunt down all the bits to uninstall manually (for a more complex install anyway). And that's why the uninstall script is welcome!
Hope that helps a little.