Restart your computer. If your screen still freezes or Zoom still crashes after a restart, check if the camera works in a Mac app, such as Photo Booth or Facetime. If it works elsewhere, uninstall the Zoom client and reinstall the latest version from our Download Center.
Safe mode also worked for me but that's not a daily-use option. Following a hunch based on virtual camera issues discussed here (https://bugs.chromium.org/p/chromium/issues/detail?id=1379392) I found that uninstalling the Zoom client, deleting the contents of /Library/CoreMediaIO/Plug-Ins/DAL/, and then reinstalling the client, did the trick. Just posting, in case it helps others...