Cook the pasta according to the package directions, then drain and set aside.
In a large skillet over medium heat, warm the olive oil. Add the onion and sauté until soft.
Toss in the garlic, bell pepper, broccoli, mushrooms, and zucchini. Cook until the vegetables are tender.
Pour in the cream and vegetable broth. Stir well and let it simmer until the sauce thickens slightly.
Season with salt, pepper, and red pepper flakes if using.
Add the cooked pasta to the skillet, tossing to coat it evenly in the sauce.
Sprinkle with Parmesan, garnish with parsley, and serve immediately.