This is a ZIP files of 4 of my favorite Zwift workouts. I use these with riders at all levels to varying degrees. All you need to do is extraxt the files and upload them to Zwift using these intructions.
 
You could use these as a weekly training plan (assuming no other ride time) or work these in as appropriate. Contact me if you'd like to dial in the perfect mix of workouts for your goals, or check out my TrainingPeaks smart trainer plan HERE (these sync to Zwift automatically when you sync your Zwift and TrainingPeaks accounts)