I understand it isn't a contact method. What I mean is, you have to explain more in detail about the process. You are just telling him "They sell to those people" without giving any information that he is really looking for.
I assume you mean like this:
The Zip Code itself is worthless. The only time a Zip Code has value is if the user completes a subsequent section of the offer/website. The CPA company pays you for the Zip Code, because through their testing 30% of users will fill out their Phone Number and Email Address AFTER they enter their Zip Code.
If a user only enters their Zip Code and disappears, the information is worthless. But if you have someones Zip Code, AND their email/phone number, you can sell them much more highly targeted products/services which they are much more likely to purchase.
Is that what you mean?