Step 1: Prepare the Lemon Herb Marinade. In a medium bowl, whisk together 1/4 cup olive oil, fresh lemon juice, lemon zest, minced garlic, dried oregano, dried thyme, paprika, 1/2 teaspoon salt, and 1/4 teaspoon black pepper. Stir well until all ingredients are combined.
Step 2: Marinate the Chicken. Add the chicken pieces to the marinade, ensuring they are fully coated. Marinate in the refrigerator for at least 30 minutes, or for up to 4 hours for maximum flavor.
Step 3: Prepare the Vegetables. While the chicken marinates, preheat your oven to 400°F (200°C) or prepare your grill for medium-high heat. Chop the zucchini, bell peppers, and red onion into bite-sized pieces. If using cherry tomatoes, leave them whole.
Step 4: Season and Roast the Vegetables. Place all the chopped vegetables and cherry tomatoes into a large bowl. Drizzle with 1 tablespoon of olive oil, a pinch of salt, and pepper. Toss to combine. Spread the vegetables in a single layer on a large baking sheet (use two if needed to avoid overcrowding). Roast for 20-25 minutes, or until tender-crisp and slightly caramelized. Flip them halfway through for even cooking.
Step 5: Cook the Chicken. If grilling, remove the chicken from the marinade, shaking off any excess. Discard the remaining marinade. Grill chicken over medium-high heat for 6-8 minutes per side, or until cooked through and internal temperature reaches 165°F (74°C). If baking, you can add the chicken directly to the baking sheet with the vegetables during the last 15-20 minutes of their cooking time, or bake separately until cooked through.
Step 6: Rest and Serve. Once cooked, transfer the chicken to a cutting board and let it rest for 5 minutes before slicing. This helps retain the juices. Combine the chicken with the roasted vegetables. Garnish with fresh parsley or cilantro if desired. Serve immediately.