Dear Expert Zenners...

I need your help in adding the sub-zone to increase the shipping cost accuracy.

It will look like this:

The sub-menus on Location and Taxes in admin area will be like this: Country; Zone (State); Sub-Zone; Sub-Zone Definition; Tax Classes; Tax Rates.

The shipping cost will be calculated based on the Sub-Zone Definition.

Thank's before, for those who help me on this...