Bring a large pot of lightly salted water to a rolling boil.
Boil the fettuccine until cooked through yet firm to the bite, about 8 minutes; drain and transfer pasta to a large serving bowl.
Heat the butter and garlic in a large skillet over medium-high heat; stir in the sausage, tomatoes, broccoli, bell pepper, mushrooms and green onion.
Cook and stir until the sausage is browned and vegetables are tender.
Stir in chicken, shrimp, white wine, cajun seasoning, milk, and 1/4 cup Parmesan cheese. Cook and stir until shrimp until they are bright pink on the outside and the meat is no longer transparent in the center, 3 to 5 minutes.
Serve over pasta and sprinkle with pepper and 2 tablespoons Parmesan cheese.