Heat the olive oil in a large skillet over medium heat.
Add the diced onion and sauté for 3-4 minutes until softened.
Add the minced garlic and cook for 1 minute until fragrant.
Add the ground beef to the skillet and cook, breaking it apart with a spoon, until browned and cooked through, about 6-7 minutes.
Drain any excess fat from the skillet if necessary.
Add the diced zucchini, dried Italian seasoning, salt, black pepper, and crushed red pepper flakes to the skillet.
Cook, stirring occasionally, until the zucchini is tender but still slightly crisp, about 5 minutes.
Remove the skillet from heat and sprinkle the grated Parmesan cheese over the top.
Stir gently to combine the cheese with the beef and zucchini mixture.
Serve warm.