Preheat oven to 475 degrees. Place tortillas on two large baking sheets. Brush with 1 tablespoon oil and sprinkle with cheese. Bake until cheese is melted and tortillas are crisp, 3 to 5 minutes.
In a large skillet, heat 1 tablespoon oil over medium-high. Add garlic and zucchini; season with salt and pepper. Cook, stirring frequently, until zucchini is crisp-tender, 2 to 4 minutes. Add shrimp and cook, stirring frequently, until shrimp are opaque throughout, about 3 minutes. Stir in lime juice. Spoon shrimp mixture over tortillas and top with sour cream and scallions.