You can find the demographics for each ZIP Code in your territory with sales territory mapping software.
The default territory export in the territory manager gives you the geography of your territories but not the demographics for each individual ZIP code (or other base geography, e.g. Counties). This article will explain how to find the demographics for every ZIP code that is in your territories, but this process works the same for territories made from any other geography.
1. Export your territory list to excel (right-click in the territory manager and choose “export territory list to excel”).
2. Open the file using File>Open.
3. Go to Dataview>Table>Join and join your territory list to the 5-digit ZIP code layer.
4. Go to Selection>Select by List and use the Territory field at the bottom of the list.
5. Choose your new selection from the pulldown in the selection toolbar and click the 
button in the same toolbar to export your selection to Excel.
For a tutorial on how to use the Territory Manager, please see the tutorial video on creating territories.
For more information on how to use joins, please see video tutorial on data joins.