Heat olive oil in a large skillet over medium heat.
Add the chopped 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 6-8 minutes.
Drain excess fat from the skillet if necessary.
Add the diced zucchinis to the skillet and cook for 5 minutes, stirring occasionally, until they begin to soften.
Stir in the diced tomatoes with their juice, dried oregano, dried basil, salt, black pepper, and crushed red pepper flakes.
Reduce heat to low and simmer the mixture for 10 minutes, stirring occasionally, until the zucchini is tender and the flavors are well combined.
Remove from heat and sprinkle grated Parmesan cheese evenly over the top before serving.