Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
Cut the chicken breast into 1-inch bite-sized pieces and chop the bell peppers, zucchini, and red onion into similar uniform sizes.
In a small mixing bowl, whisk together the harissa paste, extra virgin olive oil, lemon juice, minced garlic, sea salt, black pepper, and ground cumin until well combined.
Place the chicken pieces and chopped vegetables onto the prepared baking sheet and pour the harissa marinade over them.
Toss everything thoroughly with your hands or tongs to ensure every piece is evenly coated, then spread the mixture out into a single layer.
Roast for 20 to 25 minutes, or until the chicken is cooked through and the vegetables are tender with slightly charred edges.
Remove from the oven and serve immediately while hot, optionally garnishing with fresh herbs if desired.