Bring a large pot of water to a boil. Generously salt the water, and cook the pasta according to package directions. Drain, and rinse the pasta under cool water.
In a large bowl combine the pasta, tomatoes, mozzarella, zucchini, basil and onion. Pour over the vinaigrette and 1/2 cup olive oil and season generously with salt and pepper. Toss, transfer to a serving bowl, give a final drizzle of olive oil and serve.
Notes
According to Wikipedia, the phrase was first used by journalist Ralph Carpenter to describe a close game in the Southwest Conference (football) tournament finals in 1976, referring to the way almost every opera ends. Ralph actually said "the opera ain’t over until the fat lady sings." This now pretty much doubles my sports reference capacity.