Heat 1 tablespoon of olive oil in a wok over medium-high heat. Add the sliced chicken breast and cook until browned and cooked through, about 5-7 minutes.

Add the remaining olive oil to the wok. Add the bell pepper, zucchini, and red onion. Stir-fry for about 5 minutes until they start to soften.

Add the cherry tomatoes and spinach, and stir-fry for another 2-3 minutes until the spinach wilts.

Return the cooked chicken to the wok. Add balsamic vinegar, garlic, oregano, salt, and pepper. Stir well to combine and cook for an additional 2 minutes.

Serve hot, garnished with fresh herbs if desired.