Bring a large pot of water to a boil and cook pasta according to package directions.
While pasta water is heating, begin cooking sausage and cook until browned. Transfer to a cutting board and slice.
In the same pan that you cooked the sausage in, heat olive oil over medium heat. Add garlic, crushed red pepper and red onion. Cook until fragrant, about 1 minute. Stir in zucchini and mushrooms. Cook 3 minutes or until slightly softened. Return sausage to the pan and pour chicken broth over the top.
By now pasta should be just about done. Strain and toss hot pasta with the vegetable mixture. Stir in cheese and toss until it melts. Season to taste with salt. Serve.