Veggie Sausage Strata

INGREDIENTS

• 2 pounds bulk Italian sausage
• 2 medium green peppers, coarsely chopped
• 1 medium onion, chopped
• 8 eggs
• 2 cups milk
• 2 teaspoons salt
• 2 teaspoons white pepper
• 2 teaspoons ground mustard
• 12 slices bread, cut into 1/2-inch pieces
• 1 (10 ounce) package frozen chopped spinach, thawed and squeezed dry
• 2 cups shredded Swiss cheese
• 2 cups shredded Cheddar cheese
• 1 medium zucchini, cut into 1/4-inch slices