Phone: Asus Zenfone 2 ZE551ML
Long story short: I tried to install official firmware upgrade using TWRP > Install > .zip. The installation was going on for a couple of minutes and then the screen blacked out. Since then, the phone does not boot.
So, I got bored of my Android 5 and decided to install a custom ROM, but I had to upgrade official firmware before that.
At first, I dove into how to install custom ROM tutorials, so I did the rooting first:
I downloaded a BootLoaderUnlocker program from the official Asus website and unlocked the BL. Then, I followed a tutorial for one-click-root, and succeded. Then I installed TWRP and flashed the Recovery to the latest available img for my phone and tried to install the Lineage OS 14.1 but got status 7 error, meaning something is incompatible.
This post states, that in order to install Lineage OS 14.1 I have to have a firmware at least MM 4.21.40.xx which is Android 6, so I went to the official Asus website and downloaded the Firmware upgrade. Since, I probably had the wrong BL at that point, I flashed the bootloader with TWRP for Z00A (Lollipop)
2.8.7.3 from here, which is the same website from which the post suggest to download a BL for MM (Android 6). I thought, since I currently have the Lolipop, should install the BL for that, just to be sure. Then I started the firmware upgrade, which rebooted the phone into the BL, I didn't think, and just pressed Normal Boot and the phone booted as usual in the old Android. Then I tried to initiate the instalation again but couldn't (it's supposed to auto-detect the file in the storage root), so I got an idea to just boot the Recovery, maybe it will continue. So, I did that, and the TWRP showed up (I forgot about it already and thought that the instalation would just continue), so I just pressed Install and chose the firmware upgrade zip manualy. The installation was going on for a couple of minutes and then the screen blacked out.
Since then, the phone does not boot. If I try to, it vibrates like it is going to boot, but then nothing happens (not even a logo).
I even tried to disconnect the battery: removed all the screws, removed the back panel and manually disconnected it. When I put it back the phone vibrated like it was going to boot, but nothing happened again.
P.S. I tried to boot into the Recovery, but that just does not work, and even did not work before the firmware upgrade (I googled, that I must press power and volume up and hold until the logo appears, but that doesn't happen).
upd: plugged into the charger, periodically shows the battery icon on the screen.