Preheat oven to 375° and lightly oil a 2-qt. baking dish. Heat oil in large skillet over medium-high heat. If using beef, sauté beef until cooked through and no longer pink. Remove from pan with slotted spoon and reserve. Add zucchini to skillet and cook until tender but not brown. Stir in corn and black beans and cook to heat through. Stir in rice, scallions, and reserved beef. In a small bowl, beat together sour cream, eggs, chili powder, and hot sauce. Pour vegetable mixture into baking dish and top with sour cream mixture. Top with corn chips. Cover dish and bake 40 minutes. Uncover and bake an additional 5 – 10 minutes. Let rest at least 5 minutes before cutting.