Find your way through the Zope source tree
How to search and find stuff in the Zope source tree
Grep and find are fine for one-time searches, but they take a lot of time, especially for a source code tree the size of Zope. Using cscope you can generate a "tags" database, which you can then search for strings and definitions of classes and methods. To generate the tags database use the pycscope package and navigate and search this database using the KScope application.