[Asus ZenFone 3 Deluxe ROMs, Kernels, Recoveries, &] adwinp:
Ladies & Gents, please buckle up for liftoff.

[COLOR="Red"][B]/* Disclaimer
* You are choosing to test this software as-is & accept full responsibility in case
* it will not work as expected. Or for WW3. Or dead kittens, whichever is worse.
*/[/B][/COLOR]

Instructions 1/2 = Bootloader Unlock:

[b]1: DOWNLOAD[/b] the [URL="https://drive.google.com/file/d/0B8rpJsF4EG0YUHh4UEo5ZExHWjg"]> prerequisites <[/URL]

[b]2: UNZIP[/b]
You will have 3 folders for zs550kl, zs570kl & zs570klpro containing:
UL-Z016-WW-4.12.40.9999-user.zip -> unlock-capable firmware update
UL-Z016_1-WW-4.12.40.9999-user.zip -> unlock-capable firmware update for the zs570kl PRO variant (in its own folder)
UnlockTool.apk -> unlock app, needed for the actual operation
PDF with Instructions in CN & EN (for zs570kl/pro only)
- bootroot.img - rooted boot image (bootrootn.img for ZS550KL Nougat)
- bootstock.img - stock boot image, if you want to return to stock or if something went wrong (bootstockn.img for ZS550KL Nougat)
- Superuser.apk - superuser app

[b]3: FACTORY RESET[/b] via Settings -> Backup & Reset
This usually solves the issue with not being able to unlock due to a "missing PIN"
Do through initial setup - no need to configure anything as the following factory reset will erase everything again.
Just click through the options to access the app drawer asap.

[b]4: COPY Files:[/b]
ZS570KL - Copy UL-Z016-WW-4.12.40.9999-user.zip to your internal storage
ZS570KLpro - Copy UL-Z016_1-WW-4.12.40.9999-user.zip to your internal storage
[COLOR="DarkOrchid"]ZS550KL - no files needed at this stage. Just ensure you are on the latest firmware: (Marshmallow: v12.40.108.29; Nougat: v22.40.26.43); update otherwise.
[URL="http://dlcdnet.asus.com/pub/ASUS/ZenFone/ZS550KL/UL-Z018-WW-12.40.108.29-user.zip"]> latest MM firmware <[/URL] put it in the root of your internal storage.
[URL="http://dlcdnet.asus.com/pub/ASUS/ZenFone/ZS550KL/UL-Z018-WW-22.40.26.43-user.zip"]> latest N firmware <[/URL] put it in the root of your internal storage.[/COLOR]
Copy & install UnlockTool.apk

[b]5: REBOOT[/b]; You should have a notification about a new firmware.
No notification for ZS550KL if you were already on the latest firmware.
Install & reboot again.

[b]6: Run the UNLOCK[/b] App
It should do another factory reset on success.

Instructions 2/2 = ROOTING:

[b]7:[/b] Copy/install Superuser.apk

[b]9:REBOOT into BOOTLOADER[/b]; either holding volume up + power from a powered down state or typing the following in a console (assuming you have ADB enabled in developer options)
adb reboot bootloader

[b]9: FLASH[/b] bootroot.img via fastboot
fastboot flash boot bootroot.img (you can also do a fastboot boot bootroot.img without flashing to check if the boot image works for you)
fastboot reboot
note: change the filename to bootrootn.img if you want to test the ZS550KL Nougat version.

[b]10:[/b] Check for root via adb shell; su or via any app requiring root, on device (terminal, titanium backup, etc...)
- in case something goes wrong, flash the stock boot via fastboot.
- report success/failure in this thread.

[b]11:[/b] BUSYBOX (Optional):
I've bundled busybox with the boot image; follow the commands below to install (in an adb shell or terminal session):
mount -o remount,rw /system
busybox --install -s /system/xbin/

[b]12: RECOVERY[/b] (Optional):
[URL="https://drive.google.com/file/d/0B8rpJsF4EG0YZ1FQSkUxRW9TdWs"]> stock dump <[/URL]
> twrp < / WIP