Hold simultaneously. Release when the phone vibrates. Flash Firmware:
You must use firmware that matches your device's SKU (e.g., WW for Worldwide, CN for China). Mixing SKUs will cause failure. Method 1: Using MicroSD Card (Recommended for ZE620KL)
Ensure your phone is charged to at least 15% (ideally higher) to prevent shutdown during the process. Zenfone 5 Firmware Downgrade
This process will erase all data on your phone. Back up everything before starting.
Once complete, select "Wipe data/factory reset" , then "Wipe cache partition" , and finally "Reboot system now" . Method 2: ADB Sideload (For Older Zenfone 5 Models) Hold simultaneously
Use volume keys to navigate to and press Power to select. Select your downgrade file.
This is the standard official method for ZenFone 5 (ZE620KL) users wanting to downgrade from Android 10 to Android 9. Mixing SKUs will cause failure
Type adb sideload [filename].zip (where [filename] is the name of your downloaded firmware).