Welcome to the forums,
For simplicity you might want to run these as two separate virtual machines.
Zimbra is an email-server uses it's own customized instances of a serious collection of software packages - OpenLDAP, MySQL, Apache, Tomcat, Jetty, Postfix, Lucene, Verity, ClamAV, SpamAssassin, DSPAM (though off by default) Amavisd-new, Aspell, James/Sieve, Perdition, NGINX, etc.
For access, there is an excellent AJAX web-client, often referred to as 'advanced'. A light/basic html only web-client called 'standard'. A mobile web-client 'MobileEdition'. Though this isn't to be confused with OTA
MobileSync which allows you to store content on your pda/smartphone.
ZDesktop which uses the same interface, but you can interact offline & all your changes are synced. There are also
connectors for outlook, apple isync, evolution, etc. And of course you can always use IMAP or POP with any other thick-client.
The short rundown:
ZCS System Architecture - ZimbraWiki
The longer rundown:
/pdf/Zimbra Architectural Overview.pdf
Search the fourms for SugarCRM and you will find a bunch of threads-here's a recent post:
/forums/zimlets/10588-sugarcrm-zimlet.html
From the sugar forums:
New thread:
SugarCRM Forums - Zimbra Integration with Sugar
Old thread:
SugarCRM Forums - New Project : Zimbra - SugarCRM Integration
A start of a zimlet:
SourceForge.net Repository - [zimbra] Index of /trunk/ZimbraWebClient/WebRoot/zimlets/sugarcrm