I figured this out. Instructions below in case anyone else needs this.
1) I created and uploaded values = Area Code, Time Zone, State, Description (I used the company field for this) into the prospect object. I had the prospect object activated so I could use it for de-duplication rule usage.
2) I created a multi-table deduplication rule in data tools. Contacts to Prospects. Comparison field was the first x characters of business phone. I returned the Time Zone in the Prospect record that matched.
3) Set the deduplication handler set to match on destination, and update field with the timezone value from the matched record.
4) Add the deduplication rule within the program step.
Works perfectly.