Heat the oven: Preheat to 425°F (220°C). Line a large rimmed sheet pan with parchment for easy cleanup.
Mix the marinade: In a bowl, whisk olive oil, lemon juice, red wine vinegar, garlic, oregano, thyme, smoked paprika, red pepper flakes, salt, and black pepper.
Season the chicken: Pat chicken dry.
Add half the marinade to the chicken and toss to coat. Let it sit while you prep the veggies (5–10 minutes).
Toss the veggies: On the sheet pan, combine red onion, peppers, zucchini, and cherry tomatoes. Drizzle with the remaining marinade and toss right on the pan.
Add chicken to the pan: Nestle the chicken among the veggies.
Keep everything in a single layer so it roasts, not steams.
Roast: Bake for 18–22 minutes, until chicken is cooked through (165°F/74°C internal temperature) and veggies are tender with caramelized edges.
Add olives and feta: Scatter Kalamata olives and feta over the pan. Return to the oven for 3–4 minutes to warm through and slightly soften the cheese.
Finish and serve: Squeeze fresh lemon over everything. Sprinkle with chopped parsley or dill.
Taste and adjust salt and pepper. Serve with warm pita, rice, or a crisp salad.