01 - Bring a large pot of salted water to a rolling boil. Cook the fettuccine according to package directions until al dente. Reserve 1/2 cup of starchy pasta water before draining. Set the drained pasta aside.
02 - Pat the chicken pieces and shrimp dry with paper towels. Season both lightly with salt and freshly ground black pepper on all sides.
03 - Heat 1 tbsp olive oil in a large skillet over medium-high heat. Add the seasoned chicken pieces in a single layer and sauté until golden brown and cooked through, approximately 5 to 6 minutes. Transfer to a plate and tent loosely with foil.
04 - Add the remaining 1 tbsp olive oil to the same skillet. Sear the shrimp for 2 to 3 minutes, flipping once, until they turn pink and become opaque throughout. Remove and set aside with the chicken.
05 - Reduce the heat to medium. Melt the butter in the skillet and sauté the minced garlic for about 1 minute, stirring constantly, until fragrant and lightly golden.
06 - Pour in the heavy cream and bring to a gentle simmer. Stir in the Parmesan cheese, lemon zest, lemon juice, crushed red pepper flakes, salt, and black pepper. Let the sauce simmer for 2 to 3 minutes, stirring frequently, until it slightly thickens and coats the back of a spoon.
07 - Return the chicken and shrimp to the skillet. Add the cooked pasta and toss thoroughly to coat every strand in the creamy sauce. Splash in reserved pasta water as needed to reach your preferred consistency.
08 - Fold in the chopped fresh parsley and taste for seasoning, adjusting with salt and pepper as needed. Divide among plates and garnish generously with freshly grated Parmesan and lemon wedges on the side.