@joshuayang
Yes, i can see what you have done and it seems reasonable, but i cant think of a way to use it for determining the shipping cost based on the zipcode. This solution works for you, because you filter the clients by country, not by zipcode. I think it should be something similar, but while digging into the code i come to think that it isn't really that easy to achieve, as it is with your case.

@Ajeh
I've searched the entire forum, but honestly didn't find the post you mean, so i guess it must been one with a country based zones. As i said, i would be extremely grateful if you can give me a hint or point me to something similar that was already done. For my case it is really important to do such shipping table, because otherwise i must set a really high price on flat shipping that would scare most of my customers ;).

Thanks in advance for your help!