I have exactly you same issue, my microphone does not work... I did reset my phone, Asus Help please!!!
a little bit everythingMaybe make a backup of apps in system local backup do it on sd card and then do the clean install via sd card https://www.asus.com/us/Phone/ZenFone-6-ZS630KL/HelpDesk_BIOS/
After upgrading to Android 10 the microphone during a call does not work. The caller can hear me when I use the speaker phone. Call also functions normally after I turn off speaker phone. I have to toggle it on and off for caller to hear.