In a large bowl, combine the first six ingredients. In another bowl, combine the eggs, oil and vanilla. Stir into dry ingredients just until moistened. Fold in zucchini and chips.
Fill muffin cups three-fourths full. Bake at 350° for 20-25 minutes or until a toothpick inserted near the center comes out clean. Cool for 5 minutes before removing from pans to wire racks to cool completely.
Mix together milk, yogurt, powdered sugar and vanilla. Pour over warm or cooled muffins.