[Zope] From Zope 2.5.1 to Zope 2.7.6

[Tim Suter]

I am upgrading our current Zope from 2.5.1 to Zope 2.7.6.  I have the
new version installed as a different instance on a different server.
The Zope 2.5.1 is in tact and what I am wondering is, how do you migrate
everything from the older to the newer?  I thought exporting the .zexp
out of Zope 2.5.1 would be ok.  However, when I import it into the new
install, it isn't the same as the original.  For example, I exported
knowledge.zexp from the 2.5.1 and imported into the 2.7.6.  Now, when I
go to pull up the page that points to info related to this data, the
subtopics are now listed below the contents of the original page.  In
looking at the html (I am no HTML expert at ALL), it did not appear that
there was even anything related to subtopics.  It must be a control from
within the Zope management interface.  

I guess I just want to know how to migrate properly with little
administrative effort.

Thanks,
Tim