Heat the olive oil in a large skillet over medium heat.
Add the chopped onion and cook 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 spatula, until browned and cooked through, about 6-8 minutes.
Drain any excess fat from the skillet.
Add the diced zucchinis, dried oregano, salt, black pepper, smoked paprika, and red pepper flakes to the skillet. Stir well to combine.
Cook for 6-8 minutes, stirring occasionally, until the zucchini is tender but not mushy.
Stir in the drained diced tomatoes and cook for an additional 2 minutes to heat through.
If using, sprinkle shredded cheddar cheese over the skillet, cover, and cook for 1-2 minutes until the cheese is melted.
Remove from heat and serve warm.