Preheat oven to 350°.
Combine first 4 ingredients in a medium bowl. Add turkey; toss gently to coat.
Cut each bread piece in half horizontally. Spray cut sides of each piece with cooking spray. Place bread slices in a single layer on a jelly-roll pan. Bake at 350° for 12 minutes or until toasted. Spread 1/2 cup turkey salad over each bottom half. Top with zucchini slices, roasted peppers, and spinach; drizzle with dressing. Spread mustard over top halves of bread; place on top of sandwiches. Cut each sandwich into 4 wedges.