This article is a great start, and if memory serves, Zapata figures into it to, somewhere along the line. You may the find the itself useful for your topic, to.
Just in case the link doesn't come through, the site is
the article is titled
The War on Terrorism's Gravy Train
Cheney's Former Company Wins Afghanistan War Contracts
The site quite obviously has an agenda but you'll find the key things that adress your topic are easily verifiable, ie. Haliburtons relationship with the administration. Things you may not be able to find out are Chenney's role and who else competed for these contracts, which are open ended budget items, and how Haliburton won the contracts. Reason being, Dick Chenney refuses to go on record with any of this nd the GOA recently dropped their lawsuit trying to compell him to.