Zello Walkie Talkie is accessible with VoiceOver and all buttons are clearly labeled, but changing the setting of the PTT button might be something you want to do in case you hate double tapping and holding on the screen for so long.
STEPS
1
Double tap the Menu button.
2
Double tap Settings.
3
Double tap Push to Talk button.
4
Choose an option:
* press and hold
* toggle (meaning double tap on the screen to talk and double tapping again to stop.)