Cook the pasta in a large pot of boiling, salted water until tender but still firm, 8 to 9 minutes.
Drain well.
Meanwhile, cut the zucchini in half lengthwise, and then crosswise into 1/4-inch-thick pieces.
Combine the zucchini and the tomato sauce in a medium saucepan over medium-high heat
Cook, stirring occasionally, until the zucchini is tender and the sauce is heated through, 3 to 4 minutes.
In a large serving bowl, combine the ricotta cheese and about 2/3 of the mozzarella cheese.
Add the pasta, pour the sauce on top.
Add the salt and pepper.
Toss well.
Sprinkle with the remaining mozzarella cheese and serve immediately.