01 - Preheat the oven to 425°F. Line a baking sheet with parchment paper or foil for easy cleanup.
02 - In a large bowl, whisk together olive oil, Italian seasoning, garlic, oregano, red pepper flakes (if using), lemon zest, lemon juice, salt, and pepper.
03 - Pat the chicken breasts dry with paper towels. Add them to the marinade and toss to coat well.
04 - Add the zucchini, cherry tomatoes, and red onion to the bowl and toss gently to coat in the marinade.
05 - Arrange the chicken breasts on the prepared baking sheet. Scatter the zucchini, tomatoes, and onion around the chicken in a single layer.
06 - Roast for 22–25 minutes, or until the chicken is cooked through (internal temperature reaches 165°F) and vegetables are tender.
07 - Remove from the oven. Sprinkle with Parmesan cheese and fresh basil or parsley before serving.