Preparation Prepare barbecue (medium heat). Brush peppers, zucchini, and bread on both sides with oil. Sprinkle lightly with salt and pepper. Grill peppers and zucchini until slightly charred and just tender, turning often, about 6 minutes. Transfer vegetables to foil-lined baking sheet. Grill bread until lightly charred and just crisp, turning often, about 3 minutes. Transfer to sheet with vegetables and cool. Tear bread into 1-inch pieces. DO AHEAD Vegetables and bread can be made 2 hours ahead. Let stand at room temperature. Cut peppers lengthwise into 1/2-inch-wide strips, then crosswise into 1/2-inch pieces. Cut zucchini lengthwise in half, then crosswise into 1/2-inch pieces. Place in large bowl. Add cucumber, tomatoes, green onions, olives, mint, and cilantro and toss to combine. Add bread pieces. Whisk 1/2 cup oil, lemon juice, and cumin in small bowl to blend. Season dressing to taste with salt and pepper. Add dressing to salad; toss to coat. Add feta and gently mix into salad. Transfer salad to large bowl. Serve, passing ground sumac for sprinkling over, if desired.
Preparation Prepare barbecue (medium heat). Brush peppers, zucchini, and bread on both sides with oil. Sprinkle lightly with salt and pepper. Grill peppers and zucchini until slightly charred and just tender, turning often, about 6 minutes. Transfer vegetables to foil-lined baking sheet. Grill bread until lightly charred and just crisp, turning often, about 3 minutes. Transfer to sheet with vegetables and cool. Tear bread into 1-inch pieces. DO AHEAD Vegetables and bread can be made 2 hours ahead. Let stand at room temperature. Cut peppers lengthwise into 1/2-inch-wide strips, then crosswise into 1/2-inch pieces. Cut zucchini lengthwise in half, then crosswise into 1/2-inch pieces. Place in large bowl. Add cucumber, tomatoes, green onions, olives, mint, and cilantro and toss to combine. Add bread pieces. Whisk 1/2 cup oil, lemon juice, and cumin in small bowl to blend. Season dressing to taste with salt and pepper. Add dressing to salad; toss to coat. Add feta and gently mix into salad. Transfer salad to large bowl. Serve, passing ground sumac for sprinkling over, if desired.