Prepare mashed potatoes according to package directions. Keep warm.
Meanwhile, sprinkle chicken with Greek seasoning. Cook chicken in hot oil in large skillet over medium-high heat 7 to 8 minutes on each side or until done. Remove from skillet, and keep warm.
Reduce heat to medium. Add zucchini and onion to skillet, and sauté 2 to 3 minutes or until tender. Add tomatoes, and cook, stirring often, 7 to 10 minutes or until slightly thickened. Remove from heat, and stir in butter and next 3 ingredients.
Serve chicken over potatoes. Spoon sauce over chicken and potatoes. Serve immediately.
Note: For testing purposes only, we used Ore-Ida Mashed Potatoes, Cavender's All Purpose Greek Seasoning, and Hunt's Fire Roasted Tomatoes Diced With Garlic.
This dish was simple and amazing. I used chicken breasts as husband doesn't like thighs. Followed recipe exactly, except served with egg noodles. The tomato, zucchini and onion mixture was amazingly flavorful! Will definitely make again.