What are some strategies for customizing Zwifts advanced workout scheduling to optimize performance gains for cyclists with diverse goals, such as endurance, sprinting, and hill climbing, and how can users effectively integrate these workouts into their overall training plan to achieve a balance between consistency and progressive overload? Are there specific Zwift features, such as the ability to create custom workouts or sync with training plans from third-party apps, that can enhance the effectiveness of these workouts, and if so, how can users leverage these features to maximize their training time?