Heat the olive oil in a large pot over medium heat. Add the ground beef and cook until browned, breaking it apart with a spoon. Drain any excess fat.
Add the onion and garlic to the pot. Cook for 3 to 4 minutes until the onion softens.
Stir in the oregano, basil, thyme, salt, and black pepper. Cook for 1 minute to wake up the herbs.
Pour in the diced tomatoes and beef broth. Bring the mixture to a simmer.
Let the stew simmer uncovered for 15 minutes to blend the flavors.
Add the zucchini slices. Cook for 5 to 7 minutes until the zucchini is tender but not mushy.
Ladle the stew into bowls and top each serving with grated Parmesan cheese.