How about using PKUnzip with a command line call. You don't make it clear whether you want to do it at the end of the test or after QTP has completed its run - in which case you need to run the test under the control of another interface (e.g. QC or VBScript) which can invoke the unzip on completion.
If you had to identify, in one word, the reason
why the human race has not achieved, and never
will achieve, its full potential that word would be "meetings".