Sound & Video for Participants
It gets a little more complex for participants:
Be in the Zoom meeting window, not just the one that shows your video
Find the "participants" button at bottom. Click it.
You should see a list of participants on the R side of the window.
Click on each to mute or unmute them, as well as start or stop video (and other options) from the drop-down menu.
image courtesy of Stony Brook University.