The update is rolling out with firmware version V15.0405.1711.76, and it brings Picture-in-picture mode, AutoFill, Notification dots, Instant apps, UI design, a fully redesigned emoji set, adaptive icons for consistent icons, and more. Also, after the update, you’ll notice some important changes to the launcher.
It’s also worth mentioning Asus ZenFone 4 users will now be able to install apps from unknown sources: “hostile downloader apps can’t operate without permission; users now permit the installation of APKs per-source.”
The update released on December 29, so it may take up to a week to arrive on all ZenFone 4 devices. If you do no get it, you can manually check for it by go to Settings > About > System Update.