In the interface options of the game you can set the camera distance to a maximum of 30. With this script you can set it higher than that, but not higher than 50, because this limit is hardcoded since some patches.
Code:
/console cameraDistanceMax 50
There is also a way to go higher than 50, but this requires you to restart the game. Open your world of warcraft folder and then go to \WTF\Account\(insert account name here)\(insert server name here)\(insert character name here)\ and open the file camera-settings.txt. It should be like "cameraDistance 24.549988" and you can edit the number, an example would be:
After you've done this, save the file, restart the game and log in with the character where you change the camera distance. But be aware of the fact, that if you try to zoom out ingame, the camera distance resets to your limit (30 or 50 with the script above). However, you can zoom in slowly if 200 is too much. I actually like this for making videos
Have fun