How do I get a sandbox environment?

I have an application that's moving into production soon, which is integrated with Zoom and Salesforce.

Once the app is in production,  I'll need a Zoom sandbox environment to make ongoing improvements without risking downtime of my production application.

How do I get a Zoom sandbox environment?

I've submitted 3 tickets to various support channels, all of which were summarily closed.

I'm completely befuddled that this isn't obvious.

Literally every other major system I've ever used offered some way to test their applications before shipping releases.