: Flashing requires putting the device into Emergency Download (EDL) Mode . While in this mode, the screen remains black, but a red LED often indicates it is ready for a firmware push via a PC.
: Installing custom firmware requires unlocking the bootloader. This can typically be initiated in Developer Options by enabling OEM unlocking and USB debugging , then using ADB commands like fastboot oem unlock . zte axon m z999 firmware best
ZTE Axon M (Z999) , the "best" firmware experience remains the official stock Android 8.1 (Oreo) : Flashing requires putting the device into Emergency
"Legacy Firmware Maintenance for Dual-Screen Devices: A Case Study of the ZTE Axon M Z999" This can typically be initiated in Developer Options
Custom firmware development for the Axon M is limited because third-party ROMs rarely support the "Extending" or "Dual" screen modes effectively.