In a very large nonstick skillet heat oil over medium-high heat. Add onion and pepper. Cook and stir for 2 minutes. Add zucchini. Cook 2 minutes more. Add shrimp, 1 teaspoon cumin and a dash of salt. Cook 2 to 3 minutes more or until shrimp are opaque.
Meanwhile, in a medium microwave safe bowl combine corn, remaining 1/4 teaspoon cumin and dash salt. Heat until steaming hot, about 4 minutes. Stir in cilantro.
Assemble fajitas with tortillas, shrimp mixture, and cheese. Serve with corn mixture.