The ASUS Zenfone 2 sounds like it might be old since we know of other Zenfone numbers that are higher. However, this is a new smartphone that runs Android 5.0 Lollipop out of the box. If you are running Lollipop and would like to know how to get root access to unchain the system internals, read the guide after the drop. Here’s how to root ASUS Zenfone 2 on Android Lollipop:
You need to have the Zenfone 2 and not any other variant of Zenfone. Furthermore, we only recommend following this guide for Android 5.0 Lollipop users. The current exploit might be patched in future software updates which means you might need to find a new rooting method.
BEFORE WE BEGIN
- Download the ASUS USB Drivers  to your computer. You need to reboot the Windows PC after installing the ASUS drivers to get them working.
- Enable the Zenfone USB Debugging Mode by heading to Settings > Developer Options > USB Debugging. Those of you who cannot find the Developer Options probably must unlock the hidden menu by heading to Settings > About Device > tap the build number seven times.
- You are voiding the warranty by following this guide. Try downloading a stock firmware to unroot and gain the warranty back.
HOW TO ROOT ASUS ZENFONE 2 ON ANDROID LOLLIPOP
- Download fastboot  to the desktop of the computer.
- Download the pre-rooted image . Look for the model number of yours and click the corresponding link from that page.
- Extract both files above to the desktop of the computer so you can use the files inside. All you need to do is right-click the mouse over the zipped file and select the extract option.
- Move the mouse to inside the Fastboot folder and right-click and hold down the Shift key on an empty white space. You should get a new menu popping up. Select to open the command prompt from that new menu.
- Type the first command: “adb reboot-bootloader”.
- Rename the system image to “system.img”. You find that image inside the other folder that isn’t Fastboot.
- Type the second command: “fastboot flash system system.img”
- Type the final command after the earlier one finishes: “fastboot reboot”
Now you have the root access you desire and the Zenfone smartphone will reboot so you can use it in normal mode. You can now get ready to clash a custom recovery image to learn how to flash a custom ROM, or you can head directly to Google Play and download the apps that need root access.