While scheduling a Zoom Meeting, check Mute participants on entry (under Advanced Options) to mute all meeting attendees as they join your meeting.
During a Zoom Meeting the host or co-host(s) can mute or unmute all participants through the Manage Participants feature.
Select Manage Participants
At the bottom of the Participants panel, you select either Mute All or Unmute All
If you want to keep your participants muted, select More and then uncheck Allow Participants to Unmute Themselves from the drop-down
To mute or unmute specific participants during your meeting, select the Mute or Unmute button next to their name in the list.