Heat the olive oil in a large skillet over medium heat until shimmering but not smoking.
Add the finely chopped onions and sauté for about 2-3 minutes until soft and translucent. Stir in minced garlic and cook until fragrant, about 30 seconds.
Incorporate the ground beef, breaking it apart as it cooks. Season with salt, black pepper, cumin, smoked paprika, oregano, and optional red pepper flakes; cook for 5-7 minutes until browned and cooked through.
Stir in the diced bell pepper and zucchini, cooking for about 5 minutes until slightly tender yet vibrant in color.
Mix in halved cherry tomatoes and sliced kalamata olives; cook for an additional 2 minutes to meld flavors.
Remove from heat; fold in fresh parsley and lemon juice before serving hot, topped with crumbled feta cheese and optional toasted pine nuts.