Heat olive oil in a large skillet over medium heat.
Add diced onion and cook for 3 minutes until softened.
Add minced garlic and cook for 1 minute until fragrant.
Add ground beef to the skillet and cook, breaking it up with a spoon, until browned and cooked through, about 6-7 minutes.
Drain excess fat from the skillet if necessary.
Add diced zucchini, dried oregano, salt, black pepper, and crushed red pepper flakes to the skillet. Stir to combine.
Cook for 5 minutes, stirring occasionally, until zucchini is tender but still slightly crisp.
Stir in the drained diced tomatoes and cook for an additional 2 minutes to heat through.
Sprinkle shredded cheddar cheese over the top, cover the skillet, and cook for 2 minutes until the cheese melts.
Remove from heat and serve warm.