Combine cheeses,zucchini and onion,mix well.Shape into rectangles 2 inches long and 1 inch thick. Cover;chill in refrigerator several hours or overnight. Or you can pat out the mixture and cut into shapes with a cookie cutter.
Combine flour,salt and pepper. Beat eggs,add salt and pepper. Dip zucchini in flour,then in egg,coat with breadcrumbs.Fry in hot oil until golden brown.Serve immediately.