Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Cut the chicken breast into 1-inch cubes and chop the broccoli, bell pepper, and zucchini into uniform, bite-sized pieces.
Place the chicken and vegetables onto the prepared baking sheet, then drizzle with the extra virgin olive oil.
Sprinkle the garlic powder, smoked paprika, sea salt, and black pepper over the mixture and toss thoroughly with your hands to ensure every piece is evenly coated.
Spread the mixture into a single layer, ensuring the chicken and vegetables aren't overcrowded so they roast rather than steam.
Bake for 18 to 22 minutes, or until the chicken is cooked through and the vegetables are tender with slightly charred, golden edges.
Remove from the oven, drizzle with fresh lemon juice, and transfer to a bowl.
Top with the sliced avocado and serve immediately while warm.