Preheat broiler with rack 6-inches from the element.
In a large, broiler-safe skillet over medium-high heat, melt together butter and olive oil until foaming subsides. Add garlic and red pepper flakes (if using) and stir until fragrant, about 1 minute. Stir in scallions, lemon zest, salt, and pepper. Add wine, reduce heat slightly, and simmer for 2-3 minutes.
Remove from heat and add shrimp, tossing to coat them with the butter mixture. Arrange shrimp in a single layer. Place pan in oven and broil shrimp for 3-4 minutes per side, until they are pink and opaque. Do not overcook.
Stir in lemon juice and parsley. Serve over pasta, rice, or with crusty bread to dip into the butter sauce.
