ZE550KL Bootloop, Fastboot and Recovery Accessible

[musooo]

Hi everyone,

I just got this phone with peculiar condition.
It keeps restarting on Asus Logo. I can access fastboot and recovery though.
I've tried flashing stock ROM (UL-Z00L-WW-21.40.1220.1998-user.zip and UL-Z00L-WW-21.40.1220.2196-user.zip) but still it keeps restarting.
After tinkering a bit, I am able to unlock the bootloader and flashed TWRP. Tried reflashing stock ROM, but still bootlooping.

Any ideas how to fix this?