Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper for easy cleanup.
Cut the chicken breast into 1-inch bite-sized cubes and chop the broccoli, bell pepper, and zucchini into uniform pieces.
In a small mixing bowl, whisk together the olive oil, lemon juice, minced garlic, rosemary, thyme, salt, and pepper.
Place the chicken and vegetables in a large bowl, pour the lemon-herb marinade over them, and toss until every piece is thoroughly coated.
Spread the mixture in a single layer across the prepared baking sheet, making sure not to crowd the ingredients so they roast rather than steam.
Roast in the center of the oven for 20 to 25 minutes, or until the chicken is cooked through and the vegetables are tender and slightly caramelized.