Cook pasta in boiling, salted water.
In a large frying pan, heat oil and saute zucchini until lightly browned, about 5 minutes. Season with salt and pepper and transfer to an oiled shallow casserole dish.
Preheat oven to 350° F.
When pasta is almost cooked, drain and add to zucchini. Add tomatoes, olives, Parmesan, rosemary and 1/2 of the mozzarella. Sprinkle with a little more salt and pepper if desired and gently mix together.
Cover with the remaining mozzarella and bake until cheese is melted and the top slightly browned, about 15 minutes.