Pat the chicken dry and season both sides with salt, black pepper, and paprika or Italian seasoning.
Heat 1 tablespoon olive oil in a large skillet over medium-high heat.
Add the chicken and cook until golden on both sides and nearly cooked through. Remove from the pan and set aside.
Add the remaining olive oil to the same skillet. Add onion and cook until softened, about 3 minutes.
Add broccoli and cook for 3–4 minutes, then add bell pepper and zucchini.
Stir in garlic and cook for 30 seconds until fragrant.
Return the chicken to the skillet and cook for 3–5 more minutes, until the chicken is fully cooked and vegetables are tender-crisp.
Taste and adjust seasoning. Finish with lemon juice or fresh herbs if desired and serve hot.