Add the Zoom URL field to the reservation page Layout and Reservation Form
To show the Zoom URL field on the reservation form and the reservation record page, you need to take the following steps:
Go to Setup - Object Manager and find the Reservation object.
Go to Page layouts - there drag the Zoom Join URL field to the page layout and save.
Go to Field Sets - Add the Zoom Join URL field to the field set that you are using on your reservation type and save.
As a FYI; The “Zoom Start URL” field also exists, this is added for possible future extensions of the Zoom App. For now you can just use the “Zoom Join URL”