Pat shrimp dry with paper towels and season lightly with salt and pepper.
Heat olive oil and 1 tablespoon of butter in a large skillet over medium heat. Add minced garlic and red pepper flakes (if using). Sauté for 1–2 minutes until fragrant but not browned.
Add the shrimp in a single layer. Cook for 1–2 minutes on each side until pink and opaque. Avoid overcooking.
Reduce heat to low. Add the lemon juice, lemon zest, and remaining 2 tablespoons of butter. Stir until the butter melts and the shrimp are well coated.
Sprinkle with chopped parsley and serve immediately. Great over pasta, rice, or with toasted bread for dipping.