Asus announced that the new Asus Zenfone 5Z will be updated to the latest Android 9 Pie by Jan 2019 but forgets to mention the update schedule for its super successful smartphone Zenfone Max Pro M1.
As per chat with Asus technical team, the Asus Zenfone Max Pro M1 aka ZB601KL is expected to receive the new Android 9 Pie update by end of Feb 2019. Further, the customer service representative also confirms that currently, the OTA update is under testing phase.
Anyway, we have to wait longer for the official Android 9 Pie update to hit your Zenfone Max Pro M1. Asus is also launching the new Zenfone Max Pro M2 and Zenfone Max M2 in India later next week which are also running on older Android 8.1 Oreo.