The latest Android 10 (Q) ROM (beta) for this phone allows to unlock the bootloader. This is somehow unofficial because there is nowhere mention of it.To get there you can just follow my guide on this forum.
My guide was for the Zenfone5 (without z). The latest official ROM for your device can be found here (on this Support Page ). If Asus follows the same policy like with the Zenfone5 it could be possible that with the latest ROM-Version the manual unlo...
If you install LineageOS based crDroid ROM, maybe you would want to install Gapps having the "Google Setup Wizard " (eg nikGapps Omni-package) which allows you to restore your Google-Backup.