ZWO files are Zwift Workouts. Fit files just record activity data. It’s not possible to convert between the two formats because they hold completely different types of information.
From what I understand, TrainingPeaks uses a CSV file format for uploaded custom workouts. While it is *potentially* possible to open a ZWO and rearrange all the data so it’s in an acceptable CSV format, it’d be quite the undertaking.
AppleTV works a bit differently than most other devices Zwift supports because it doesn’t have persistent storage. Files often get moved around from location to location on the internal storage media and the only thing that keeps track of file locations is the operating system itself. While our developers are working on bringing custom workouts to AppleTV, it’s the same limitation that prevents Zwift from being able to upload workout files to TrainingPeaks.
It’s nothing I can specifically recommend, but it’s likely there are scripts and utilities you can use to convert ZWO workout files to CSV, but it’d still require having to move your ZWO files from your AppleTV to a PC or a Mac first.