or simply use wget directly from your Zimbra server:

wget http://www.zextras.com/download/zextras_suite-latest.tgz

this URL will always point at the latest release of ZeXtras

• Now that you have downloaded ZeXtras Suite, a few simple steps are required to get it up and running.
• STEP 1: As ROOT, unpack the file you just downloaded inside a directory (we suggest in /root/) in your Zimbra server.
• STEP 2: Enter the directory created by the unpacking of the file.
• STEP 3: Run the install.sh script with the "all" option (so ./install.sh all).
• STEP 4: Once ZeXtras Suite is installed, you need to Initialize ZxBackup.
• A video tutorial to the install process can be found here.
  
• Detailed informations about the ZeXtras Suite installer can be found in the ZeXtras Suite Install Guide.
• If you need further support have a look at the ZeXtras Suite Install and Setup Forum.
• Now that ZeXtras Suite is installed, join the ZeXtras Community in the Forums.