Heat 1 tablespoon of olive oil in a large skillet or wok over medium-high heat.
Season chicken cubes with salt and pepper, then add to the skillet and cook until browned and internal temperature reaches 165F (74C), approximately 6-8 minutes.
Remove chicken from the skillet and set aside on a plate.
Add the remaining tablespoon of olive oil to the same skillet.
Add the red onion, bell pepper, and zucchini to the pan and stir-fry for 4-5 minutes until vegetables are tender-crisp.
Stir in the minced garlic, oregano, and thyme, cooking for 60 seconds until fragrant.
Return the cooked chicken to the skillet and add the Kalamata olives.
Drizzle with fresh lemon juice and toss all ingredients together for 1-2 minutes to incorporate flavors.
Remove from heat and garnish with crumbled feta cheese immediately before serving.