Re: gyms focusing on Courses [Zurich]
I really like the migros fitnesspark (on top: Pulse 5 and Stockerhof). They have a good selection of courses, but it is true you need to arrive early to be sure to go in.
But the best part for me is the nice sauna and hot pool area. So if you are late for the course just go on the thread-mill by yourself and then indulge in the hot tub.