
You can either contact your IT admin or uninstall and re-install Zoom from the official website here.

If you see that the option has been greyed out, it could be a corporate policy setting. If you’re on Mac, just go to Zoom Preferences > Share Screen tab and untick the box next to “Enter full screen when a participant shares screen.”

Note that the steps are more or less similar for macOS. Zoom will no longer switch to the full screen whenever a participant in the meeting decides to share their screen.
