Bring a large pot of salted water to boil. Add linguine or spaghetti and cook according to package instructions until al dente. Reserve 1/2 cup of the pasta water, then drain and set aside.
In a large skillet, heat the olive oil and 2 tablespoons of butter over medium heat. Once the butter has melted, add the minced garlic and red pepper flakes. Sauté for about 1 minute until fragrant but not browned.
Add the shrimp to the skillet. Season with salt and pepper. Cook for about 2-3 minutes on each side until the shrimp are pink and opaque.
Reduce heat to low. Add the lemon juice, lemon zest, and the reserved pasta water to the skillet. Stir to combine. Add the cooked pasta and remaining 2 tablespoons of butter, tossing everything together until well combined and the butter melts.
Stir in the chopped parsley, adjusting seasoning if necessary.
Plate the shrimp scampi, garnishing with additional parsley and Parmesan cheese if desired.