Some of Zoom's screen share features (e.g., the whiteboard) require
display compositing. If you encounter a black window when sharing
the screen, then one of the following actions should help:
- Enable compositing in your window manager if it is supported
- Alternatively, run the xcompmgr command (from x11-misc/xcompmgr)

To enable screen sharing on GNOME Wayland, edit ~/.config/zoomus.conf
and change the value of enableWaylandShare to true.