If you need to change Zimbra web-port like 80 or 443, you can use following commands to change it:

#su - zimbra
#zmprov ms server.hostname zimbra MailPort port
#tomcat stop (or Apache)
#tomcat start (or Apache)

or

#su zimbra
#zmprov mcf zimbraMailPort port
#tomcat stop (or Apache)
#tomcat start (or Apache)
#zmprov gcf zimbraMailPort  //to show the existing listening port