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 uniform 1-inch pieces and chop the broccoli, bell pepper, and zucchini into bite-sized chunks.
In a small mixing bowl, whisk together the olive oil, lemon juice, lemon zest, minced garlic, dried oregano, sea salt, and black pepper.
Place the chicken and all the chopped vegetables onto the prepared sheet pan.
Drizzle the lemon-herb marinade over the chicken and vegetables, tossing thoroughly with your hands or tongs to ensure every piece is well-coated.
Spread the mixture out into a single, even layer on the pan, making sure not to overcrowd the ingredients so they roast rather than steam.
Roast in the center of the oven for 18 to 22 minutes, or until the chicken is cooked through and the vegetables are tender with slightly browned edges.
Remove from the oven and garnish with fresh parsley or an extra squeeze of lemon juice before serving warm.