Besides the Android 7.0 Nougat and its features, the new update (build number 14.2015.1701) will improves touch performance as well as enables FET VoLTE and VoWiFi on Zenfone 3. In addition, the update adds a bundled notifications switch and removes some existing Zenfone features (because of incompatibility with Android Nougat).
Because the OTA update is rolled out in phases, it will take a week or more to get the Nougat update notification across the Zenfone 3 (ZE520KL/ZE552KL) variants. If you do not received the update notification, then go to Settings > About > System Update > and check for update manually.
Once the update is available, follow the instructions to install the Android 7.0 Nougat update on Zenfone 3.
How to Install Android 7.0 Nougat Update on Zenfone 3
1. Make sure at least 1.5GB free space on the internal storage of your Zenfone 3.
2. Once update is available, tap on this notification to download the update.
3. Once download is completed, a pop-up to install the update will appear. Tap Install to continue.
4. The device will reboot twice during the installation of the update. Please do not turn off the device until the home screen appears.