In a hot skillet with a little oil, saute 1 chopped onion and sliced zucchini. Meanwhile, cook the penne pasta to al dente. In another skillet, add sausage and chorizo slices. Let cook on low heat for 5 minutes, stirring frequently. Add some crushed tomatoes and 1 tablespoon of tomato paste. Simmer for another 10 minutes. Add salt and pepper to taste. Drain the pasta and add to the sausage tomato preparation. Garnish with parsley, and serve with grated Parmesan.