Why did you install tomcat? Zimbra hasn't used tomcat since the 4.5 release series. In addition, Zimbra installs all the component software it needs, or notes which things it requires you to install during the installation process. I'd be fairly certain, however, that installing tomcat would most definitely interfere with Zimbra, since it would use the same ports as Zimbra's jetty processes (mailboxd). I would advise you to freshly install your OS, and then only install those things that the zimbra installer tells you it needs installed.
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