On the laptop with cinnammon… it was disabled already. Tried playing with other settings without luck. Have to troubleshoot the hybrid grafics card issue and post another thread, last system update borked my system due to python upgrade and optimus. 
will see if troubleshooting that will fix the flickering screen share on zoom too.
The easiest would be if someone else with cinnamon can test and confirm the zoom screen sharing works flawlessly. Perhaps which install method they used.
Looks like xfce and kde are good to go. Which means zoom should work on both qt and gtk based DE.
I used cinnamon on this laptop because the other DE did not enable me to deal with high dpi screen issues, moved over recently from kde, see my thread.