Yes, it can be done!
If your zip-codes have 4-digits, then create a menu, click the "green plus" (add a key sequence). Enter "????".
In this way, the call will pass on when the dialer has entered 4 digits. These 4 digits are now held in the $KEY variable.
You can now test the $KEY variable in the "Condition Editor". You'll have to check up against each possible zip-code, or you can use smaller than/larger than comparisons.
You should be able to work it out from here ;-)