Wheh you install Zimbra it will check for port conflicts with other applications such as Apache, MySQl and allow you to change the ports Zimbra uses. In a test environment it doesn't really make much diffreence whether other services are running on the same box (depending on the number of clients connecting) but for a production system it is advisable to install it on a stand-alone server.
The Zimbra install shoudl take about 10/15 miutes to get up and running, it does on my system but that's not running any other services.
