01 - Heat olive oil in a large deep skillet over medium heat. Add Italian sausage and cook, breaking it apart with a wooden spoon, until thoroughly browned and cooked through, approximately 5 minutes. Transfer sausage to a plate and set aside.
02 - In the same skillet, add chopped onion and diced bell pepper. Sauté for 3 to 4 minutes, until softened. Incorporate minced garlic and diced zucchini, and continue to cook for an additional 2 minutes.
03 - Stir in the dry orzo pasta and toast for 1 minute, stirring constantly to prevent sticking.
04 - Add canned diced tomatoes with juice, broth, Italian herbs, red pepper flakes if using, salt, and black pepper. Bring the mixture to a boil.
05 - Reduce heat to a gentle simmer. Return cooked sausage to the pan, cover, and cook for 10 to 12 minutes, stirring occasionally, until orzo is tender and most liquid is absorbed.
06 - Fold in chopped spinach and half the shredded mozzarella cheese. Stir until spinach wilts and cheese is melted.
07 - Sprinkle the remaining mozzarella and all the grated Parmesan over the skillet. Cover and allow to sit off the heat for 2 minutes until the cheese is melted.
08 - Serve hot, garnished with additional Parmesan or fresh basil as desired.