As of version 4 of our ZoomConnect (aka Mindbody + Zoom) integration you can now choose to prevent possible forwarding of Zoom participant join links to others.
Doing so, you can turn off the ZoomConnect Zoom meeting setting "Allow multiple devices":
This will prevent using the Zoom participant link on multiple devices and therefore using it by other people.
NOTE: Please be aware, that this Zoom setting prevents usage of the participant join link on multiple devices in general. If your client has a problem using the join link with his/her computer and would like to switch to another device, this will not work due to that setting.