Heat 1 tablespoon olive oil in a skillet over medium heat; cook and stir sausage until browned and crumbly, 5 to 7 minutes. Transfer sausage to a bowl.
Heat 1 tablespoon olive oil in the same skillet; cook and stir mushrooms and onion until onions are softened and mushrooms are softened yet still firm, about 5 minutes. Add chicken broth and asparagus; cook and stir for 3 minutes. Season mixture with salt and pepper.
Move vegetables to the edge of the skillet and add half-and-half, flour, and butter; cook and stir until a thick and smooth sauce forms, 5 to 7 minutes. Add sausage to the skillet and stir vegetables into sauce.
Bring a large pot of lightly salted water to a boil. Cook fettuccine in the boiling water until tender yet firm to the bite, 1 to 3 minutes; drain.
Heat remaining 1 tablespoon olive oil in a separate skillet over medium heat; cook and stir garlic until fragrant, about 30 seconds. Add zucchini noodles (zoodles) and red pepper flakes; cook and stir until tender yet firm to the bite, 5 to 7 minutes. Mix fettuccine into zoodle mixture.
Divide zoodle-fettuccine mixture among serving plates and top with sausage mixture. Sprinkle Parmesan cheese over each.
