Cheddar, Beef and Zucchini Pie

3/4 lb lean (at least 80%) ground beef

1/2 cup chopped onion (1 medium)

1/2 cup chopped green bell pepper (1/2 medium)

1 1/2 cups sliced zucchini (1 large or 2 small)

1 tablespoon all-purpose flour

1/8 teaspoon pepper

1 1/2 cups shredded Cheddar cheese (6 oz)

2 Italian plum tomatoes, sliced

3 eggs

1 tablespoon Dijon mustard

1 cup half-and-half or milk

1/2 teaspoon salt