I want to train a new employee on how to take help desk calls

Hi @jndavid 

Inbound calls: If you are in a zoom meeting and a phone call comes in, you will be notified and you can accept it. Keep in mind the Audio for whoever accepts the call, will switch from the zoom meeting to Zoom phone. Once the phone call is  completed, you can switch the audio to join back the meeting. This is the experience. 

While making outbound calls, Yes, you can invite the external party via Participants -> Invite -> Zoom phone and the dialer will be presented

Hope that helps. If this response helps, please accept the answer as an accepted solution, so others can benefit as well.