Heat oil in large skillet over medium heat. Add sausage, zucchini, and onion; cook and stir 8 minutes.
Stir in rice, diced tomatoes (with juice), corn, chili powder, oregano, and salt. Simmer over low heat 10 minutes, stirring occasionally. Remove from heat.
Top with cheese; cover. Let stand 5 minutes, or until cheese is melted. Serve immediately.