We have had this question a couple of times now. How is it possible to index a discussion forum that is created by the PHPBB script?
You can index PHPBB forums but you need to skip a lot of irrelevant pages.
For example you need probably don't want to index the members list, profile pages, private message pages, login pages, etc, etc..
So you need to add a list of pages to skip to the Zoom configuration window, on the 'Skip Options' tab.
Here is an example list that you can copy and paste into the Zoom skip list.
This will cause Zoom to index topic pages (as apposed to individual posts) and assumes you have the forums in the sub-directory called /forum.
This was tested with PHPBB version 2.0.13