post
https://gateway.us.zip.co/orders//refund
Refunds funds for the specified order and allocates them to the payment plan to apply it to the customer. If sync query parameter is set to true, replies synchronously with callback payload, otherwise, replies asynchronously on callback URL.
Default sync value is false for asynchronous behavior.
If you are a pay-on-ship/DFC merchant, you can only apply up to your captured amount.