All the products I sell in my zen-cart are over 300lbs and require freight shipping. I'm trying to setup flat shipping rate based on state, or zip code. Since shipping to California and Florida, for example will have different flat rates, what is the best way to set this up?

I have also tried setting as attributes, but I think that will confuse the customers.

Is there a way to set this up as a zone rate?

I want to have a dropbox of prices for 50 states and one flat international price for everywhere else.