John just had an extra 'ZimbraWebClient/WebRoot' tacked on there - call it switching between dev & compiled binaries mindset
I do that by mistake all the time.
The path in source:
BRANCH/ZimbraWebClient/WebRoot/public/launchZCS.jsp
On your machine becomes:
/opt/zimbra/jetty/webapps/zimbra/public/launchZCS.jsp
We've got a speed test up at:
Lets Talk Speed, Chrome, and WebKit » Zimbra :: Blog