Asus ZenFone 2 ZE550ML is about to get the Android 5.1 Lollipop treatment soon. A user’s chat with an Asus representative confirms that the update is in final testing.
The support guy confirmed to him that Asus is currently working on the Zenfone 2 5.1 update, and that it’s under final testing stage right now. See the screenshot below. working with model num Z550EL, one that sports HD display.