Place beans and peppers in a greased 13-in. x 9-in. x 2-in. baking dish. Top with tomatoes, cheese and zucchini. In a bowl, combine the biscuit mix, salt, cayenne, eggs and milk just until moistened. Pour over the vegetables.
Bake, uncovered, at 350° for 55-60 minutes or until puffed and a knife inserted near the center comes out clean. Let stand for 10 minutes before serving.