Good day, @larry9.
I can share some insights about entering a zip with letters for the credit card info.
For a credit card holder who has an address located outside of the United States, we recommend you get in touch with your bank. They can provide you options using their international card with U.S. based businesses that require a 5-digit numeric zip code and details about the fee.
To get more details, you can check this article: Cannot take an international credit card due to invalid zip code.
Please know that the Community has your back should you need anything else. Have a blissful day!