Let vendor choose where their items can be sold.
If a country isn't associate with a zone and a person from that country try to buy a product, shipping isn't added to the price which is understandable. The problem is that the person still can buy the product!
If no shipping method is associated with buyer location, Quick2Cart should warn the buyer that shipping isn't available for his location and offer the buyer to contact the seller.
I think this is a very important feature.