Chicken Shawarma with Green Beans and Zucchini

Name: Chicken Shawarma with Green Beans and Zucchini
Ingredients: 1 pound zucchini, sliced 1/4 inch thick; 1/2 pound green beans; 1/2 cup extra-virgin olive oil; Kosher salt; 1 1/2 teaspoons ground allspice; 1 1/2 teaspoons ground black pepper; 1/2 teaspoon ground white pepper; 1/4 teaspoon cinnamon; 1/4 teaspoon ground cumin; 1/4 teaspoon ground coriander; 6 skinless, boneless chicken thighs; 1 garlic clove, minced; 1 cup plain low-fat yogurt; 2 tablespoons fresh lemon juice; Six 6-inch pitas, split horizontally; 1/2 small red onion, thinly sliced