Potato Zucchini Frittata

Name: Potato Zucchini Frittata
Ingredients: 2 Tablespoons cooking oil; 1/2 cup chopped onion; 1 medium zucchini, quartered and sliced; 2 cups frozen O’Brien hash brown potatoes, thawed; 1 teaspoon salt, or to taste, divided use; 1/2 teaspoon pepper, or to taste, divided use; 1 10-ounce can original Rotel, drained; 7 large eggs; 1 teaspoon smoked paprika; 1/2 teaspoon Mexican oregano; 1/2 teaspoon red pepper flakes, optional; 1/4 cup whole milk; 1/4 cup sour cream; 1 1/2 cups shredded Cheddar cheese; Sliced green onions, fresh parsley and tomato slices