[ZC554KL] How to downgrade system from Android P to Android O target version
*Please be aware that after install this system image on a device, all the personal data will be erased, so please remember to back up your data first.
Step 1: Please prepare a MicroSD Card and insert to your phone and copy the downgrade image file into the root directory of the MicroSD card.
Step 2: Power off the device.
Step 3: Long press with＂Power＂ key and ＂Volume Down＂ key together for at least 5 seconds to enter Recovery Mode.
Step 4: Please use＂Volume Down/Up＂ key to select menu on the screen. Choose＂Apply update from SD card＂, then press ＂Power＂ key to enter the selection.
Step 5: Search for the downgrade file and choose the selection of ＂Volume Down/Up＂key, then press ＂Power＂ key to enter the selection, the downgrade image file will start to process.
Step 6: When the updating process is done, Choose＂Wipe data/factory reset＂and tap＂Yes＂ to perform the master clear.
Step 7: Select＂Reboot system now＂ to finish the process.