Mix mayonnaise, yogurt, lemon peel and 1/4 teaspoon each of the basil and marjoram in small bowl until well blended. Cover. Refrigerate until ready to serve.
Mix ground bison, egg, garlic powder, sea salt, pepper and remaining 1/2 teaspoon each basil and marjoram in large bowl until well blended. Shape into 4 patties. Brush zucchini slices with oil.
Grill over medium heat 4 to 6 minutes per side or until burgers are cooked through (internal temperature of 160°F). Grill zucchini slices 1 to 2 minutes per side or until tender.
Serve burgers on rolls topped with tomato, zucchini and herbed spread.