ok, here we go... wait, first I should note that I've never tried this and that it would be very difficult to do.
Download this -
liveHTTPHeaders - extension for firefox, once you have it installed you'll want to pull up your favorite zip/email offer page. Open liveHTTPHeaders and then submit a zip/email in the form.
Now the liveHTTPHeaders extension will spew out a shit load of information, you'll want to scroll back up and take a look at the POST request sent right after you submitted your email/zip.
There's going to quite a bit of information in this POST request so you'll have to do a little analyzing. Basically, you're making sure that the POST request hasn't sent anything encrypted back to the servers, because we can't do anything with that. If the POST request looks simple, like it's submitted a few static variables (e.g. campaign number, aff network id, email, zip, IP, etc...) then you can probably try to mimic it.
If you succeed and get nothing like FJDLS(FJDSKL4589340589043KLF

S or other encrypted shit (like a key) sent then continue.
Go in and grab all the information for the from html tags from the initial zip/email offer page. Copy it to a test page. Then you're going to want to make sure that when you submit the form it doesn't call any javascript (besides normal email/zip validation). If it does, you'll have to pull that javascript and put it on your page too.. just experiment until it actually lets you submit to their "2nd page submit" area...
Let me know if this works, or if you have any questions - I'll give them a shot.
You're going to need hella fucking luck to get this to work, as it depends on lots of variables. It also depends on a bit of mad coder skillz, so again, good luck.
Tob