Universal ZipCode plug-in is the most complete and feature rich ZipCode plug-in for nopCommerce, which can be used to offer a functionality using which your visitors can check if their delivery location is served by you or not, and whether your shop allows for COD (Cash on Delivery) as payment option for their location.
They can find this detail directly on the Product Detail pages, so there are less chances of dropout from the checkout page. The plug-in also helps with finding locations that you are currently not serving, but your store visitors are requesting. So you can add services for those locations.
You can ask visitors about their zip code on their first visit to your on-line store. And once they enter, they won't need to check it again, as the plug-in persists the same.
The plug-in also helps you restrict visitors to checkout with non serviced zip code as well as disables COD payment method when COD is not available.
You can maintain a list of zip codes with their status for shipping and COD in simple excel file, which can be imported directly into the nopCommerce for easier maintenance.