Google calendar/mail zoom to jitsi

Using Jitsi, Zoom, GCal, GMail, Firefox Nightly on an iMac

An email was sent to me to arrange a meeting using Zoom.
The Zoom entry in GMail and GCal was converted to a Jitsi URL.
I was unable to attend my meeting.

How did the Zoom URL get converted to a Jitsi URL?
How can I undo it?