Preheat the oven to 200°F and warm an oven-safe plate or platter.

In a small bowl, whisk together the harissa and 1/2 cup of the olive oil.

In a small bowl, combine the whole milk yogurt, cucumber, and garlic. Season to taste with salt and pepper. Transfer to a small serving bowl and set aside.

In another bowl, whisk together the labneh and za’atar. Transfer to another small serving bowl, sprinkle with more za’atar, and set aside.

Heat a grill pan over medium-high heat. When the pan is just smoking, arrange the vegetables in a single layer on the pan and grill in batches until tender-crisp, then transfer to the warmed plate. Return to the oven to keep the vegetables warm.

Generously brush the bread with the remaining 1/4 cup oil. Sprinkle with salt, then grill on the grill pan until golden brown and charred on the edges.

On a large board or platter, arrange the vegetables, bread, tzatziki, labneh, and olives and serve.