Cook the pasta in salted water until barely al dente, then drain.
Meanwhile, in a large pan add the olive oil, chopped onion and eggplant and cook over medium heat for 10 minutes partially covered, stirring every few minutes.
Add the diced sausages and all the seasonings, stir, and cook 5 to 7 minutes, stirring periodically, until sausages are getting browned.
Add the diced zucchini, and make room for them in the pan to cook for 5 minutes (or until just barely fork tender - do not overcook). If your pan is on the smaller side, you may need to transfer some of the sausage mixture to a plate while the zucchini cooks.
Add the garlic, cook another minute. Add the crushed tomatoes, stir, cook 3 minutes. Add the cooked pasta, stir, cook together for a few minutes until pasta is al dente.
Taste and season with salt or pepper if desired, or a drizzle of olive oil.
Serve and top with capers and the fresh parsley.