To install:
Download from website http://www.zimbra.com/products/desktop.html.
Extract.
$sudo install.pl
Then, run the command given for standard user.
Create another user zimbra folder.
Drag Zimbra icon from desktop to Gnome Menu.
You can check the tutorial here:
http://www.linux.com/learn/tutorials/374096-make-the-zimbra-desktop-your-email-and-social-desktop
http://www.linux.com/learn/tutorials/374096-make-the-zimbra-desktop-your-email-and-social-desktop