Heat olive oil in a large skillet over medium heat.
Add the chopped onion and sauté for 3 minutes until translucent.
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 spatula, until browned and cooked through, about 6-8 minutes.
Drain excess fat from the skillet if necessary.
Add the diced zucchini, dried oregano, salt, black pepper, and crushed red pepper flakes to the skillet.
Stir well and cook for 5-7 minutes until the zucchini is tender but still slightly crisp.
Remove from heat and sprinkle the grated Parmesan cheese over the skillet.
Stir to combine and serve immediately.