Download latest Android Lollipop 5.0 stock firmware for Asus ZenFone Selfie ZD551KL smartphone from hereor from here.
Firmware details
Archive: Asus Zenfone Selfie Z00UDB ZD551KL 3+16
Firmware: Android Lollipop 5.0 stock
Image: Asus Zenfone Selfie Z00UDB ZD551KL 3+16
Model: Asus ZenFone Selfie ZD551KL smartphone
Image file size: 861 MB
Platform: Qualcomm Snapdragon MSM8939 Octa-Core
Caution: Please do not update firmware unless you know what you are doing, you really want it or it is absolutely necessary. Firmware updates may occasionally have bad results, like bricking your device, temporarily or permanently. The firmware update process is done entirely at your own risk. Before attempting to update the firmware, back up your data.