Want to root your new HTC Desire Z ? follow the step by step instructions below.
How to Root HTC Desire Z
Download com.modaco.visionaryplus.r14.apk and copy it in the root of your sd card.
Download and Install Astro File Manager
Run Astro File Mangager, Install the downloaded file copied in your sd card in step 1. You will be guided by the on screen instructions
After installation completes, close Astro File Manger.
Launch VISIONary app from your launcher screen.
After it completes, restart your device.
If you stuck somewhere or face any problem, let me know in comments, I will help you out.