Boil water in a large pot with a pinch of salt. Add the pasta. Cook the pasta to "al dente" (about 10 minutes). Drain the pasta.

Peel and chop the onion. Wash and chop the green zucchini and yellow squash into small pieces. Wash and chop the basil. Remove the casings from the Italian sausage (if there are any). Shred the mozzarella block.

In a nonstick stovetop pan, add the olive oil on medium-high heat. Add the chopped onions. Once the onions start to change colors (about 2 to 3 minutes), add the Italian sausage. Continue breaking up the sausage into small pieces as the Italian sausage browns (about 5 minutes). 

Add the chopped zucchini and squash to the sausage. Add some salt to taste. Cover the pot until the zucchini and squash are cooked through (about 5 to 7 minutes).

Heat the oven to 375℉ (190℃).

In a baking dish 9" x 13" or larger, add ½ of one jar of tomato sauce. Add ½ of the pasta then ½ of the sausage mixture. Pour the remaining portion of the first tomato sauce jar. Using a spoon, scoop ½ of the ricotta cheese onto the tomato sauce. Spread the ricotta gently. Sprinkle ½ of the shredded mozzarella cheese and some of the chopped fresh basil (if using).

Add ½ of the second tomato sauce jar onto the mozzarella cheese. Add the remaining pasta and sausage mixture. Equally distribute the remaining tomato sauce jar on top of the pasta and sausage mixture. Drop spoons of the ricotta cheese onto the tomato sauce and spread with the back of the spoon. Sprinkle the remaining shredded mozzarella cheese and chopped basil.

Put the ricotta and sausage ziti in a 375℉ (190℃)oven in the middle rack for 35 to 40 minutes, or until the mozzarella cheese starts to brown on top.