I want to zero out my account balance

Here are two ways you can remove all your Apple ID (Apple Account) balance:

Spend it:

If your store credit is less than the cost of a single item on the iTunes Store, App Store, or iBooks Store, and you still have a valid payment method for that country, you can add the payment method to your account [ how to add a card --> https://support.apple.com/HT201266 ]. When you buy an item, it will use the remaining store credit and the rest will be charged to the payment method.

Have Apple keep it

"If you still can't change your country or region, or you have less store credit than the cost of a single item, contact Apple Support." Apple will remove the balance and keep it.

Click here --> https://support.apple.com/choose-country-region/media-services Select your country, then a product such as billing. If you do not see your country, see if there is an "other" listing for that region. If you don't see an option that handles your issue then keep experimenting with selections until you reach one that gets you a chat session or a telephone call and get the representative to redirect you.

Or call Apple Support --> https://support.apple.com/HT201232

References:

Click on this link to read full information about requirements for changing store country:

Change your Apple ID country or region --> https://support.apple.com/HT204447

https://support.apple.com/HT202359 --> "Before you can delete your Apple ID or change your Apple ID country or region, you must spend all of your Apple ID balance. You might also have to wait for any pending refunds to process."