Preheat oven to 300 degrees F. Grease a 13x9x2-inch baking pan; set aside. In a large bowl stir together flour, cornmeal, nuts, sugar, baking powder, and salt; set aside.
In a bowl whisk together the eggs, butter, and applesauce. Stir in the corn, zucchini, cheese, and onion. Add egg mixture all at once to cornmeal mixture. Stir just until moistened. Pour batter into prepared pan.
Bake 50 to 60 minutes, just until edges are golden brown. Cool slightly; serve warm.