Asus has released the Android 9 Pie update to users of the ZenFone Max Pro M1 and the Max M2 as promised. The update is being seeded in batches and might take some time before the device shows the update notification. Android Pie update for the Max Pro M2 is expected to arrive before April 15.
https://www.notebookcheck.net/Android-Pie-update-now-rolling-out-to-Asus-ZenFone-Max-Pro-M1-and-ZenFone-Max-M2.416158.0.html