Asus will be seeding the Android 9 Pie update for the ZenFone 5Z by the end of January 2019. The new update is expected to bring new features including a new contextual pop-up volume bar and a new Magnifier for easy copy-paste.
https://www.notebookcheck.net/Asus-ZenFone-5Z-will-be-getting-the-Android-9-Pie-update-in-January-2019.365071.0.html