Preheat oven to 375°F.
Bring a large pot of water to a boil for the pasta.
Wrap spinach in a clean kitchen towel and wring out the excess liquid.
Heat about 3 tablespoons of EVOO, 3 turns of the pan, in a skillet over medium heat. Add garlic and swirl a minute; add spinach, separating it with your fingers as you put it in the pan. Toss spinach with garlic and oil, season with salt and pepper and cook to heat through.
Salt boiling water liberally and cook ziti about 5 minutes. Reserve about 1 cup of the starchy cooking water and drain pasta.
Combine ziti with spinach and garlic, ricotta, parm cheese, salt and pepper and transfer to large casserole dish. Top with mozzarella and bake until brown and bubbly, about 30 minutes.