Welcome to the forum.
ZCO is the tool you're looking for to sync a ZCS server (hosted one or your own) and Outlook 2007. It works very nicely but needs a "Network Edition Pro" licence.
Outlook 2007 and iPhone and ZCO don't get along together. At all. It's related to an Apple bug (iPhone only likes .pst files) that is not fixed yet. See here :
iPhone - iTunes - Outlook 2007
In june, Apple will release firmware 2.0 for the iPhone. This firmware will be able to sync directly to the ZCS server (as long as the server runs Network Edition and that
Zimbra Mobile is enabled for your account)