If you wish, you can do downgrade by special firmware version.
Ignore this "Software downgrade from WW-17.1810.1910.63 (Android Q)", it is because when it was released actual version was 63, but you can use for any A10 firmware release.ZenFone 6 (ZS630KL) BIOS & FIRMWARE | Phone | ASUS Global
Version Android Q downgrade to Android P
ASUS ZenFone 6 ZS630KL Software downgrade from WW-17.1810.1910.63 (Android Q) to target Image Version: WW-16.1220.1909.194 (Android P) by using MicroSD card for WW SKU only* Please follow step 6 and ensure to backup data before downgrade.
Steps of Update:
1. Prepare a MicroSD card.
2. Check software version of your device**
3. Only apply to same SKU update, Example: WW->WW, CN->CN, TW->TW, ID->ID.
4. Software update cannot transfer the software SKU.
5. Wrong SKU may cause update failure, please update the same SKU version only.
6. How to manual update firmware please refer tohttps://www.asus.com/tw/support/FAQ/1039929
*How to know the device model?
Path: Settings->About-> Model number
Example: ASUS PadFone2
**How to know the device software version?
Path: Settings->About-> software information->Build number
*System upgrade may cause part of data missing, please backup your important data before system upgrading.