Preheat oven to 400 degrees. Toss together tomatoes, 4 garlic cloves, the sugar, 1/2 teaspoon salt, 3 tablespoons oil, the thyme, and marjoram in a large ovenproof skillet (preferably cast-iron). Transfer skillet to oven, and roast until tomatoes are soft and starting to burst, about 30 minutes. Leave oven on.
Heat 2 tablespoons oil in a large skillet over medium heat. Season zucchini with salt, and arrange in a single layer in skillet. Add water, 2 pinches baking soda, and the basil. Cook, turning often, until water evaporates and zucchini is tender but not mushy, 15 to 20 minutes. Transfer to a baking dish.
Heat remaining tablespoon oil in a medium saute pan over medium heat. Smash remaining 5 garlic cloves, and add to pan. Add pine nuts, and cook, stirring until toasted, about 3 minutes. Add capers, and cook 1 minute. Stir in olives. Using a slotted spoon, transfer tomatoes to pan; discarding tomato juices, whole garlic cloves, and herbs. Season with pepper, and stir.
Arrange zucchini in a single layer in baking dish. Spoon heaping mounds of tomato mixture onto each, and pour any juices over tops. Heat rounds in oven until warm, about 10 minutes. Finely grate lemon over rounds.
Adding baking soda to the cooking water helps the zucchini retain their bright-green color.