Preheat your oven to 400°F (200°C) and line a large rimmed sheet pan with parchment paper for easy cleanup.
Cut the chicken breast into 1-inch bite-sized pieces and chop the broccoli, bell pepper, and zucchini into uniform sizes to ensure even roasting.
In a small mixing bowl, whisk together the olive oil, lemon juice, lemon zest, dried oregano, garlic powder, sea salt, and black pepper.
Place the chicken and chopped vegetables onto the prepared sheet pan and pour the lemon-herb marinade over the top.
Toss everything thoroughly with your hands or tongs to ensure every piece is well-coated, then spread into a single layer across the pan.
Roast in the center of the oven for 18 to 22 minutes, or until the chicken is cooked through and the vegetables are tender and slightly caramelized.