Asus ZenFone 2 is more stable following this OTA update
"A new system update is provided to improve stability," says the bootsplash for the update. The phone had a special U.S. unveiling last May in New York City that came more than five months after the unit was initially introduced overseas on January 5th, 2015. We expect to see the ZenFone 2 receive an update to Android 6.0 sometime in the current quarter, which ends in June.
Once you see notification that your ZenFone 2 has received the stability update, make sure that you are connected to a Wi-Fi network before you begin the updating process. Also, make sure that your battery is charged to at least 50% before starting. Because this is an OTA update, it is sent out in waves. If you haven't received it yet, don't panic. You will receive it soon.
Overall, the stability update is a good trial run for the update to Android 6.0.
source: @ArunKmRathi via AndroidCentral