Preheat the oven to 375 degrees . In a colander, toss zucchini with the salt and let drain, stirring occasionally, about 20 minutes.
Meanwhile, in a medium bowl, combine the bread crumbs with the thyme, rosemary, 1/4 cup Gruyere and the butter. Press the mixture evenly into a 10-inch springform pan and bake until set and golden, about 15 minutes. Transfer to a rack to cool. Increase the oven temperature to 400 degrees .
Using your hands, squeeze out as much liquid as possible from the zucchini. In a bowl, toss the zucchini and remaining 3/4 cup Gruyere. Season with pepper. Top the crust evenly with the zucchini mixture and bake until lightly golden, about 50 minutes. Run a knife around edge of the tart before removing the side of the pan.