Cook pasta and garlic in boiling water 7 minutes; add zucchini, and cook 3 minutes. Drain well; discard garlic cloves. Place pasta mixture in a large bowl. Add 2 tablespoons Parmesan, oil, marjoram, salt, and pepper; toss well to coat. Drop ricotta by tablespoonfuls into pasta mixture; toss well. Sprinkle each serving with Parmesan.