there are some pre-rooted stock backup forms of the system software if you want to try. you merely download them, transfer them to your phone via USB, boot in recovery mode, back up the system FIRST, and restore the new rooted version by browsing to where you saved the 'nandroid' (the name for a backup) on your storage, select it, and away you go! this can be done with or without clockworkmod recovery (which requires root) because some of these images are saved as a backup file that is restorable on any device.
these custom softwares are in the ZTE Merit---all things root subforum
for example, there is a good one known as speed-freak. here are some steps to install this one, based on restoring the image as a backup file:
1. hook the phone to your computer's USB port using the cord that came with the charger (it unplugs from the brick that plugs into the wall)
2. the computer will recognize and install some drivers, then your phone should show a 'USB storage is connected' with the android robot and a 'turn on USB storage' button. click this button, and Windows on your computer should show an autoplay prompt. click 'view files/folders on the device' option and an explorer window showing the phone's SD card contents will show (may be files and/or folders--one should be called 'downloads')
3. download the speed-freak file onto your computer and open it in WinRAR (this program is available online and is free) and extract the folder to your C: drive. accept any User account control prompts if running Vista/7 (this program requires your permission to continue)
4. browse your C: drive, should be a folder titled 'speedfreak 1.1' in there. copy this entire folder to your SD card's root directory (don't save it in another folder.)
5. click 'turn off USB storage' on the phone. you should see the normal home menu showing again. disconnect the phone from the computer. make sure the phone's battery is 100%.
6. boot the phone in recovery mode. first, hold the power button until you see three options in a pop-up. click 'power off'. the phone will shut off. now, and this is important, at the same time, hold down the menu (bottom left button), volume up key, and power button at the SAME time. you will see the ZTE logo followed by a recovery menu (hold down these three buttons until it displays). in there should be some options such as backup and restore. click backup first, and wait for that to be done. next, click the restore option (keep in mind, the touchscreen won't work in this menu, it is controlled by volume keys (scrolling up/down), and the home key selects. the image may be upside down. back key goes back a menu. when you click restore, you should either get a list of options to select a file (it depends on the recovery) or it may automatically go ahead. if you get the option to select a file, browse to the location or name 'speedfreak 1.1' and accept. the phone will show verbose gibberish and eventually say 'restore complete'. if given the option to reboot, do so. the phone will take some time to reboot, but you will see the ZTE logo, followed by a plain 'Android' logo and the main screen. it will look a bit different and you will have to re-link your Google account and reinstall your apps, but it's worth it!