1. Combine mayonnaise, salsa, Worcestershire sauce, and 1/8 teaspoon pepper in a small bowl.
2. Heat oil in nonstick skillet; add onion and half the zucchini and cook 3 to 4 minutes, until tender. Cool
3. Toss beef with zucchini mixture, Worcestershire, salt, and 1/2 teaspoon pepper. Shape into four 1/2-inch-thick patties.
4. Heat grill pan. Grill patties 5 to 6 minutes per side until an instant-read thermometer inserted into side of burger registers 160 degrees F (165 degrees F for turkey). Place burgers, sauce, and remaining zucchini inside pitas. Makes 4 servings.