In a large bowl, toss the shrimp with 3 tablespoons olive oil, the lemon juice and zest, 4 minced garlic cloves, crushed red pepper flakes, and a generous pinch of kosher salt and black pepper; let sit for 10 minutes.
Heat 2 tablespoons unsalted butter in a 12‑inch skillet over medium heat until melted.
Add the orzo to the skillet and cook, stirring often, until the orzo is slightly golden and toasted, about 3–4 minutes.
Stir in the additional 2 minced garlic cloves and cook for 30 seconds until fragrant.
Pour in 2 1/4 cups chicken stock and bring to a boil, then reduce to a simmer and cover; cook until the orzo has absorbed the liquid and is tender and fluffy, about 12–15 minutes.
Add the marinated shrimp to the skillet, stir to combine, cover, and cook until the shrimp are pink and opaque, about 5–8 minutes.
Sprinkle with 3 tablespoons chopped fresh parsley and a spritz of lemon juice; optionally stir in 1–2 tablespoons melted butter for extra richness, then serve immediately with lemon wedges.