ROM Full Firmware ASUS ZenFone 2 ZE551ML Marshmallow WW 4 21 40 223 How to OTA update ? (Go to settings>About>System Update>Check for Update ) How to update Manual ? Place to Internal Storage>Restart>Click Update How to update via ADB sideload ? Here ZENFONE 2 ZE551ML firmware: WW VERSION WW-4.21.40.223 Description ASUS ZenFone 2=ZE551ML(Z00AD/Z00ADA/Z00ADB/Z00ADC) software Image: V4.21.40.223 for WW SKU only* (andriod M) Improvement Item: 1)Improve Wi-Fi/Bluetooth stability 2)Update Security patch 3)Improve system stability 4)Support India SOS call (India only) Steps of Update: 1.Check software version of your device** 2.Download device software and Update SOP (From �Manual� Item) 3.Only apply to same SKU update, Example: WW->WW, CN->CN, . 4.Software update cannot transfer the software SKU and downgrade the software version. 5.Wrong SKU may cause update failure, please update the same SKU version only. *How to know the...