Over the past couple of weeks, a story has been breaking that video conferencing vendor Zoom leaves a back door on your Mac when uninstalling it, which will let them run their service and reinstall that much quicker in the future. For details, I recommend this Medium article.
Long story short, even if you uninstall Zoom, Zoom software is still installed and running on your Mac. This can be very easily verified by opening a terminal window and entering lsof -i :19421. On my Mac, that returned this:
Note that, after I have removed it, I again run lsof -i to confirm that it is gone. As I don’t get the same result, I have confirmed that it is, indeed, gone.
I will leave you with a caveat; if you don’t understand the commands, I would recommend you find someone who does, or at least that you do the research your self. In the words of @jdpearce: