the scenario is this: The site offers two types of shipping, one standard and one fast and the customer can choose what he wants.
The request is to apply a surcharge fixed for certain zip codes to both expeditions.
There's a nice free extension that does that: MatrixRate.
It works by importing a CSV file with zip codes, countries, weight and price. You can use a wildcard ("*") if you don't care about a certain column. It works at website scope.