How to Make It
Preheat a gas grill to medium-high (400°F to 450°F). Stir together vinegar, shallot, mustard, and honey in a small bowl, and let stand 10 minutes. Whisk in thyme, 3 tablespoons of the oil, 1 teaspoon of the salt, and 1/4 teaspoon of the pepper until combined.
Toss together zucchini, 1 tablespoon of the oil, and remaining ½ teaspoon salt and ¼ teaspoon pepper in a large bowl. Place zucchini on oiled grates. Grill, uncovered, until zucchini are tender and grill marks appear, about 2 minutes per side. Transfer to a medium bowl.
Brush remaining 1 tablespoon oil evenly over both sides of bread slices. Place bread on grates; grill until slightly charred and crispy, 1 to 2 minutes per side. Rub grilled bread on both sides with garlic halves. Discard garlic, or reserve for another use. Tear bread into 1-inch pieces.
Add tomatoes and 2 tablespoons of the vinegar-shallot mixture to zucchini in bowl, and gently toss to coat. Spoon tomato-zucchini mixture onto a serving platter. Top with torn grilled bread, and sprinkle with basil and parsley. Serve immediately alongside remaining vinegar-shallot mixture.