Copy entire phone to the same device?
To manage the system and not give it root access, you neex to use a custom recovery.

A custom recovery will allow you to backup your DATA &amp; SYSTEM Partitions so thst you can restore everything easily and safely.

The most common custom recovery in my opinion is TWRP or Team Win Recovery Project, this would be the newest most common in succession from Clock Work Mod as the most common.

I searched for TWRP for your device, and i got this installation guide... . 
Zenfone 3 &amp; 3 Delux TWRP

Once you've successfully flashed TWRP you can do the device clone that you want by going to Backup and performing a full device backup to the External SD Card.

Now install TWRP on Device 2.

Place your SD Card from Device 1 with the new backup into Device 2   

Boot into TWRP on Device 2 

Go to Restore and select External SD  

Select your backup

Restore the backup.

The second device will be entirely replaced with the data from the first device excluding some stuff like IMEI number etc, depending on your TWRP Version....



Locked Bootloader ?

Asus provides an Official unlock tool for your specific device at the Asus website...

Here's a direct link... 


  Asus Unlock Tool


Reference ;
www.asus.com/Phone/ZenFone-3....