Preheat the grill or grill pan over medium heat. Brush both sides of the zucchini and eggplant slices with the oil and seasonal well with the salt and pepper. Grill on both sides until tender and nicely browned, about 2 - 4 minutes per side.
Lightly grill or toast the ciabatta bread.
Spread the mayo on the inside of the bread. Layer with spinach, tomatoes seasoned with salt and pepper, turkey, red onion, cheese, and drizzle with balsamic glaze.