Prep the shrimp and zoodles. Pat the shrimp dry with paper towels and season with salt and pepper.
Spiralize the zucchini or use pre-spiralized zoodles. Set both aside.
Sear the shrimp. Heat the olive oil in a large skillet over medium-high heat. Add shrimp in a single layer and cook 1–2 minutes per side until pink and opaque.
Transfer to a plate. Do not overcook.
Build the base. Lower heat to medium. Add butter to the skillet.
Once melted, add garlic and cook 30–45 seconds, stirring, until fragrant but not browned.
Make the sauce. Pour in the heavy cream and bring to a gentle simmer. Stir in red pepper flakes if using. Simmer 2–3 minutes to slightly thicken.
Add cheese and lemon. Reduce heat to low.
Stir in Parmesan a small handful at a time until melted and smooth. Add lemon juice and zest. Season to taste with salt and pepper.
Toss in shrimp. Return the shrimp and any juices to the pan.
Stir to coat and warm through for 30–60 seconds.
Cook the zoodles briefly. In a separate large skillet, add a light drizzle of olive oil over medium heat. Add zoodles and a pinch of salt. Toss for 1–2 minutes until just tender but still firm. Do not overcook; they should keep some bite.
Combine and finish. Transfer the zoodles to the Alfredo skillet and toss gently with tongs to coat.
Add parsley. If the sauce seems thick, loosen with a splash of water or cream. If too thin, simmer 30 seconds.
Serve. Plate immediately with extra Parmesan and a crack of black pepper.
Add optional veggies if desired, folding in right before serving so they stay bright.