Preheat your oven to 400°F (200°C) and line three large rimmed sheet pans with parchment paper for easy cleanup.
In a very large mixing bowl, whisk together the olive oil, lemon juice, lemon zest, dried oregano, garlic powder, sea salt, and black pepper until well combined.
Add the cubed chicken breast and halved baby potatoes to the bowl, tossing thoroughly to ensure every piece is well coated in the herb marinade.
Divide the chicken and potatoes evenly across the three prepared sheet pans, spreading them out into a single layer to ensure even roasting.
Place the pans in the oven and roast for 15 minutes, allowing the potatoes to soften and the chicken to begin browning.
While the first stage roasts, toss the broccoli florets, chopped bell peppers, and sliced zucchini in the remaining marinade left in the mixing bowl.
Remove the pans from the oven and carefully add the green and red vegetables to the pans, mixing them slightly with the chicken and potatoes.
Return all pans to the oven and roast for an additional 15 to 20 minutes until the chicken reaches an internal temperature of 165°F and the vegetables are tender with caramelized edges.
Remove from the oven and serve immediately while hot, perhaps finishing with an extra squeeze of fresh lemon for brightness.