Solution for On-call drivers

Hello ​@Peggy77 
As you mentioned, I tried experimenting with creating "External Contacts” in Zoom Phone Account Settings where the list of these “Student Drivers” mobile phone will be associated with their names; after this is just a matter of maintaining that list of external contacts updated, and then redirecting an incoming call to one of those external contacts and that could be done via a Zoom Auto Receptionist by the mean of using as destination the “Routing Option” → "Route to External Contact” and select one of the external contacts you previously created. You could create Holidays and pseudo-automate in advance forwarding changes on a specific schedule, but it is always one destination at a time.

I experimented as well checking the “External Contact” option of “Treat as internal extension” to verify if it would let me select those external contacts inside a Zoom Call Queue (ZCQ) to allow distributing calls to multiple external destinations but it didn't worked. 

A more convoluted way of doing it is by develop an simple external application that updates/changes that “External Destination” for each time a call is received:

• You will configure the ZAR to forward the call to an external destination (i.e. External Contact): This will take care of redirecting the call to configured current on-call driver
• That App will be triggered by receiving a Zoom Webhook generated when there is an incoming call, and it will update the ZAR external destination by using API with a rotating pool of drivers you have previously defined.