In a large bowl, whisk together the prepared basil pesto, white wine vinegar, and olive oil and season with salt and pepper. Gently toss in the tomatoes and zucchini and set aside for ten to 20 minutes to marinate.
Set the sourdough slices out onto a baking sheet, set the oven rack to the centre position, and preheat the broiler to high.
In a small bowl, mix three tablespoons of butter with the garlic and season with salt and pepper. Spread the butter onto the sourdough slices and set under the broiler for three to five minutes or until golden.
Set a skillet over medium-high heat and add the remaining tablespoon of butter. Toss in the corn, season with salt and pepper, and cook for two to three minutes. Transfer the corn to a large bowl and spoon the marinated tomatoes and zucchini on top, allowing any excess marinade to drip off and remain in the marinade bowl. Add in the basil, parsley, half of the chives, and the lemon zest and toss to combine.
In a small bowl, mix the remaining chives, lemon juice, and goat cheese together. Season with salt and pepper and spread it onto the sourdough slices. Cut each slice of sourdough in half, if desired, and arrange on a plate. Top with the tomato, zucchini, and corn mixture and serve.