[aasasd]

Sort of sidetracking, but: afaik applications open from a browser via a custom protocol in a link, and for that the application has to be already installed—unless MacOS offers to search the app store (if it does, not sure). So, this suggests to me that either MacOS leaves protocol associations in place after uninstalling an app, and has the machinery to resurrect such an app from the backups, or Zoom leaves around a protocol-handling app after an uninstall.

[kalleboo]

As with file types, the URL protocols an app can handle are configured in the app's Info.plist. An app doesn't have to be "installed" in any special way, the app just has to be somewhere on a disk mounted where the OS can see it in order for the OS to find it.

In OPs case, Zoom.app was still hanging out in his backup, ready to be launched (Time Machine backups are just a standard disk image)

[saagarjha]

It might be possible that the uninstaller does something strange to "uninstall" the app and leaves macOS confused.