The planning done at the Defense Department changed Zinni's original conception in some fundamental ways. For example, Zinni proposed a civilian occupation authority with offices in all eighteen Iraqi provinces, whereas the Coalition Provisional Authority (CPA) was actually established only in Baghdad.
Wouldn't eighteen provinces allow a more controlled method and allow for ethnic differencs.

Add another 200,000 troops to concentrate on the worst third of the provinces and you could lock them down tight.