Key Features
It is used to flash stock firmware on any Asus Zenfone mobiles. If you download correct firmware it can be downgrade or, upgrade your mobile using Asus flash tool.
Also, the tool can be used to backup Apps.
Used to backup system apps.
Included progress bar feature.
How To Use Asus Flash Tool- Step guide
Step 1: Download Stock firmware compatible and suits with your smartphone
Step 2: InstallAsus USB drivers in your windows PC. If you already installed them, you can skip this step.
Step 3: Download and install Asus flash tool in your PC.Get the latest version from here.
Step 4: Now connect your
Step 5: Once the installation is done open it. Navigate to the main screen of the tool and find the Disconnected button and click on it.
Step 6: Once your mobile is connected to the PC, A green color connected button will appear on that same screen.
Step 7: Then you have to locate the firmware files which you have already downloaded into your PC.
Step 8: Once you select the firmware files which you want to flash, click on the start button in order to begin the flashing procedure. Then your device will restart automatically.
Step 9: Next you have to switch into the Recovery mode. Press on Volume up and volume down button for few minutes, in order to boot in the recovery mode.
Step 10: Select " Apply update from ADB" available under the recovery mode.
Step 11: Then click on the resume button to resume the flashing procedure.
Step 12: This will take 5-10 minutes to finish the flashing procedure. Once it is done disconnect the smartphone from the PC and restart it.

Developer Credit
The tool has undergone many developments in order to give the best for Asus users. However sincere thank should be devoted to Pawneshwer Gupta for making such a great attempt to develop Asus flash tool.
So hope my guide will helpful for you. Wish you Good Luck.