In a large pot of boiling salted water, cook the pasta according to package instructions; drain well and reserve 1 cup of pasta water and return to the pot to keep warm.
Prepare the grilled chicken/shrimp if using.
Meanwhile, in a large deep skillet, heat the olive oil over medium heat. Add the broccoli, red onions, red pepper, zucchini, and garlic. Season with Italian seasoning, salt, and pepper. Cook for about 4 minutes, or until the vegetables start to soften.
Add the cooked pasta, peas, milk/cream, and the reserved pasta water and stir to combine until the sauce thickens and clings to the pasta, about 1-2 minutes.
Remove from heat and stir in lemon zest, lemon juice, Parmesan cheese, and basil.
Serve in bowls garnished with extra parmesan cheese and basil, if desired.
