A Zen Cart UPS shipping module that makes use of UPS' RESTful/Oauth API; see this UPS link for the API documentation. This module replaces both the UPS and UPS-XML shipping modules. Those modules use interfaces to UPS that have been deprecated as of 2023.
Zen Cart Support Thread: https://www.zen-cart.com/showthread.php?229558-UPS-Shipping-using-RESTful-OAuth-API-Support-Thread
Zen Cart Plugin Download Link: https://www.zen-cart.com/downloads.php?do=file&id=2374