A quick look...
It seems you cannot add Zoom to an existing event, the Zoom button is
missing if you 'edit event'. We would be looking to add Zoom to our
regular monthly meetings while the lockdown is on. So we would have to
delete that event and create a new one.
I take it only the host of the meeting can create the Zoom alert. We
would have to give our host calendar permissions for this, at the
moment we have it set so that only mods can create calendar events.