Thank you for your asking. How long has the device been used? Has the device ever broken or dropped before?
First, please backup your device. If you can not access the phone, please check if your google account or microSD card have auto backup your data. [Phone] How to back up the data stored in your phone ? | Official Support | ASUS Global
It seems that you already tried to access Recovery Mode, can you check if you had followed the steps to access recovery mode for the Factory Reset as below?
1. Power off the phone, then keep pressing "volume down key"
2. Press "power key" and stop press " power key" once you feel the vibration. Still keep pressing "volume down key".
3. Stop press "volume down key" once you enter [Android Recovery] Screen
4. Choose "Wipe data/factory reset">"Yes"
5. "Reboot system now"
#Hardware Reset Guide[ZenFone] How to do hardware reset on your phone? | Official Support | ASUS Global
**Please note that once the steps are completed, all data, apps, settings and personal information will be deleted.
If you still can not access to Recovery Mode, please contact ASUS repair center in the country of your residence: https://www.asus.com/support/Service-Center-All-Countries/
If it is impossible to access the service center during Covid-19 period, please try CallUs: https://www.asus.com/support/CallUs