Here is a link on how to do it on the phone side for the Centro:
Setting up an Exchange ActiveSync (Outlook) email account on a Centro
On the Zimbra side you need to install a commercial cert (well you don't HAVE to, but it is a lot more work to go through and doing a desktop sync and upload to get your self signed cert to work. I would not want to walk someone through that over the phone.)
After you have your cert, you just plug in your username and password, mail server address and that is about it. So far all of my calendar, email and contacts sync up fine. I will post back in a few weeks with more thoughts after having used it while I go on vacation
