Unbricking a phone without being able to access recovery I have rooted my Zenfone 2 ZE551ML using a method which permanently replaces recovery (I didn't realize it back then). Can I unbrick it using only fastboot? I can't use adb, as I can't open recovery. I basically need a fastboot adb sideload alternative for flashing the entire firmware/ROM. I tried to flash every single part (except for the system.img, which I couldn't flash) of the firmware using fastboot separately, but it didn't work.
You can flash a new recovery image with fastboot.
The command is:

fastboot flash recovery recovery.img

where 'recovery.img' is the name of the image.

If you enter fasboot on the command line with no options or parameters you will see the usage, which is: 

fastboot flash [partition] [filename]