While both Xperia Z and Xperia ZL are identical hardware-wise, the steps on how to root the Sony Xperia ZL are slightly different from its cousin. For the tech folks, the CF Auto root file that used to root Xperia Z has been modified to work with the Xperia ZL. So, here are the instructions on how to root the Xperia ZL.
Requirements for rooting
1. Firmware Version: 10.1.A.1.350
2. Unlocked bootloader. Do not perform root if your bootloader is not unlocked. Followpost on how to unlock bootloader on the Xperia ZL.
3. Fastboot files. Follow this post to get it up and running. It also covers problems that you might face if you are running Windows 8.
Here are the instructions
1. Reboot into bootloader
2. Flash modded CF-Auto-Root Kernel by typing (the file cfautoroot.img will soon be made available for download)
fastboot flash boot cfautoroot.img
3. reboot from fastboot
4. Xperia ZL will now start booting and you will get indication on screen saying (phone will reboot in 10 seconds)
after CF-Auto-Root reboots device once, disconnect USB cable and do hard power off. For this very purpose, there is a special button under the ZL’s back cover. Disconnect the USB cable; press and hold the special OFF button for more than 10 seconds. The phone will vibrate 3 times.
5. Connect device in fastboot mode and flash stock kernel
fastboot flash boot insecure.img
6. Reboot device and the device will start booting into OS
7. Download busybox installer from Play Market and install it in /system/xbin/
That is it. You now have a rooted Xperia ZL.