If you have trouble hearing your cell phonewhen using zello, here is the solution.
https://www.ebay.com/itm/Ham-Radio-P...edirect=mobile
They work amazingly well. It is a speaker, mic, and ptt all in one. Connects to you cell via bluetooth. Has a clip on the back to clip to your shirt collar or epaulet. I have a set of these and they work amazingly well. Loud and clear audio, dont have to touch your phone. If cellular service is weak not holding the phone but setting it by a window such as the package tray behind the seat helps. Your hand is a shield for the antenna.