Cut zucchini and tomatoes into 1/2-inch pieces and keep vegetables separate. Chop onion and mince garlic.

In a heavy kettle heat oil over moderately high heat until hot but not smoking and saute uncooked pasta, turning occasionally, until golden, about 2 minutes. With a slotted spoon transfer pasta to a bowl. In oil remaining in kettle saute zucchini with salt to taste, stirring occasionally, until browned, about 3 minutes, and transfer to another bowl. Squeeze sausage from casings into kettle and add onion and garlic. Saute mixture, stirring and breaking up sausage, until browned, about 5 minutes. Add tomatoes, water, and wine and bring to a boil Add pasta and clams and boil, uncovered, stirring occasionally, 8 minutes, or until clams are opened and pasta is al dente. (Discard any unopened clams.) Stir in zucchini and parsley and cook until heated through.