How to Manually Update Zenfone 2 ZE551ML & ZE550ML to Marshmallow Read What's New in Marshmallow Update for Zenfone 2 Download Link for ZE550ML (Z008) download link fo ze551ml(Z00A) How to Download? Just visit the link that matches your device model. Choose Android as the OS. Expand firmware section. Choose the latest version in the 4.xx series. Example – 4.21.40.178 Method 1 – Update via ADB (PC Needed) We strongly recommend following this method to update your phone if you have access to a PC. There are lesser chances of the phone getting bricked during the update. Download & Install ADB & Drivers to your PC. Turn off your phone. Boot to fastboot mode by pressing and holding the Power & Volume Up keys. Use volume keys to choose Recovery Mode. Press power key to select. Select Apply update from ADB in Recovery Mode and connect your phone to the PC using USB cable...