Bring pasta, garlic, broth, 2 cups water, and oil to a boil in a large straight-sided skillet; season with salt and pepper. Cook, stirring frequently, 3 minutes less than instructed on pasta package.
Add shrimp and 1 teaspoon lemon zest and cook, stirring occasionally, 1 1/2 minutes. Stir in peas, 1/2 cup feta, and dill and cook, stirring, until peas are bright green and crisp-tender and shrimp are opaque, about 1 minute. Stir in lemon juice. Serve, topped with remaining 1/4 cup cheese, remaining 1 teaspoon zest, and coarsely chopped dill, and drizzled with oil.