Zoom Co-host

@Lisadowns - it is a little bit semantics, but a co-host is only assigned after a call starts.  If someone is set up prior to the meeting, they would be set up as an alternative host.  

Therefore, if you are asking how to disable someone's permission as an alternative host, you will want to go into your meeting invite on the Zoom web portal, scroll to the bottom and remove their email from the alternative host field.  If you are trying to keep someone who has helped as a co-host out of the call, there is no easy way without rebooking the call or blocking that user.  You can always decline assigning them co-host permissions, but that is at the time of the call and not in the invite itself.