Combine olive oil, lemon zest, lemon juice, red pepper flakes, and dried parsley in a small bowl. Add shrimp and toss to coat. Marinate for 15 to 20 minutes.

Melt butter in a pot over medium-high heat. Add olive oil. Stir in orzo and onion, toss to coat, and cook, stirring frequently, until onions are translucent and orzo is lightly toasted, 4 to 5 minutes. Mix in garlic and cook until fragrant, about 30 seconds.

Deglaze pot with white wine and stir until wine has cooked off. Pour in chicken broth and season with salt and pepper. Cook, stirring frequently, until orzo is tender yet firm to the bite, 8 to 10 minutes. Add peas and shrimp with marinade to the pot, cover, and cook, stirring occasionally, until shrimp are light pink, 3 to 4 minutes.

Divide between 2 dishes, sprinkle with fresh parsley, and garnish with lemon slices.