Trigger the Update: Disconnect the USB cable. A notification should appear in the status bar saying "System Update File Detected."
Asus Zenfone Selfie (ZD551KL / Z00UD) Firmware 6.0.1 Marshmallow Update Guide
Device Name: Asus Zenfone SelfieModel Number: ZD551KL (Z00UD)Android Version: 6.0.1 MarshmallowBuild Number: WW-21.40.0.2214 (or later)Region: WW (Worldwide) Key Features of Marshmallow 6.0.1 asus zenfone selfie z00ud firmware 6.0 1
Transfer the File: Connect your phone to your PC and move the downloaded .zip file to the root directory of your phone’s internal storage (do not put it in a folder).
Check Your SKU: Go to Settings > About > Software Information. Ensure your Build Number starts with "WW." You must match your current SKU (WW to WW). Trigger the Update: Disconnect the USB cable
If your phone is bootlooping or the local update fails, use this method: Power off your device.
Download the Firmware: Locate the official .zip firmware file for the ZD551KL from the Asus support website. Ensure your Build Number starts with "WW
Backup Your Data: Flashing firmware can sometimes lead to data loss. Save your photos, contacts, and messages.
Storage Space: Ensure you have at least 2GB of free internal storage. How to Install Asus Zenfone Selfie 6.0.1 Firmware Method 1: The Local Update (Recommended)
Update Notification Not Appearing: Ensure the file name has not been changed. It must remain exactly as downloaded from Asus. Also, double-check that the file is in the root directory, not the "Download" folder.Stuck on Asus Logo: This is common after a major version jump. Boot into recovery and perform a "Wipe Cache Partition."Downgrade Issues: Moving from Marshmallow back to Lollipop is difficult and usually requires a factory reset and specific downgrade tools.