Using a vegetable peeler, peel zucchini and yellow squash lengthwise into strips, pressing down firmly with the peeler so that the strips are almost as thick as a potato chip (see photo). Place vegetable strips in a large bowl. Add salt and pepper. Toss lightly and set aside.
In a 10-inch skillet, heat olive oil over medium-high heat. Add garlic and sauté, stirring constantly until garlic has softened and is transparent, about 2 minutes. Add chicken pieces and 2 Tablespoons rosemary. Stir frequently with a wooden spoon or heat-resistant spatula until chicken is cooked through and slightly browned, about 8-10 minutes. Remove chicken pieces to a medium bowl and set aside.
# Add chicken stock and remaining 2 Tablespoons of rosemary to the skillet and bring to a boil, scraping brown bits from the bottom of the pan with a wooden spoon or heat-resistant spatula. Boil until chicken stock is reduced by half, about 3-5 minutes.
Add zucchini and yellow squash strips to the skillet, stirring gently. Cook until vegetables are tender, about 5 minutes. Toss in the reserved cooked chicken along with any juices that have collected in the bowl. If desired, add grated Parmesan cheese on top. Serve immediately.
Chef's Note: Feel free to make substitutions. Instead of chicken, use thinly sliced steak or whole medium shrimp. Substitute carrots for the zucchini or squash. Instead of rosemary, try oregano, parsley or thyme. Add more flavor by replacing half the olive oil with margarine or butter. And cut your prep time by 10 minutes by using precooked chicken or leftovers.