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This instruction is for ASUS ZenFone (A400CG/A400CXG) WW sku downgrade only.


1. This tool is for firmware downgrade from Android 5.0 (Lollipop) to Android 4.4 (KitKat) V6.6.3.

2. All data stored on your phone will be deleted after downgrade. Please back up your data in advance.

3. Before performing downgrade, please ensure the battery life higher than 15%, or charge the phone during downgrade process.

4. Please first enable "Media device (MTP)" in "Settings" -> "Storage".




Please follow steps below:

1. Please go to

    and download downgrade tool




2. Connect your phone to PC via Micro USB cable, and copy the file ""

    that you just download to root directory of internal storage of your phone.



3. Detach micro USB cable from the phone to make the notification for firmware update popped up on status bar.



4. Tap "System Update File Detected" and follow steps to downgrade firmware.



5. Downgrade is completed. Check if the firmware version is V6.6.3 in "Settings" -> "About" -> "Software information".  

Version history
Last update:
‎10-14-2019 12:00 AM
Updated by: