Broadcasting Zwift to a TV can be pretty simple. Zwift does not have a button that will directly cast the game to a TV. There are two ways that I know of that you can broadcast Zwift a TV, getting an Apple TV is also a way that you can use Zwift directly on a TV. If there are more ways, let me know in the comments and I will be sure to add it.
The first way to do this is using the google home app with a google chromcast, one ofthese. The google home app if available in the app store and the google play store. Once you have it download, just setup your chromcast device by plugging it into your TV, then following the instructions here: https://support.google.com/chromecast/answer/2998456. Once you have completed that, all you have to do is chromcast your screen, open the Zwift app, then you are good to go!
The second way is by using an HDMI adapter. These are available for USB-C, iPad Chargers, and most other chargers out there. You can find them on Amazon for a relatively good price. The setup is very easy. First, plug in the HDMI cord, then plug the HDMI cord into the HDMI adapter. Finally, make sure your TV is set to whatever HDMI the HDMI is plugged into, and open up the Zwift update.