To make the red onion marmalade: In a nonstick pan or heavy skillet, heat the olive oil over medium heat. Add the onion and sprinkle with salt. Stir and cook until tender and translucent, 5 to 7 minutes. Add 1 cup water and cook for 10 minutes more, until the onion is very soft and the water has cooked off. Add the vinegar and sprinkle the onions with the sugar. Stir well and cook for 2 to 3 minutes more, until the vinegar has cooked off completely. Season with salt and set aside.
To make the zucchini chickpea fritters: Preheat the oven to 375 degrees F.
To a food processor, add the chickpeas and pulse until they are a thick paste. Transfer the beans to a large bowl and add the onion and zucchini. Use clean hands to mix well, then form the mixture into 10 cakes. Set aside.
On a plate, combine the garbanzo bean flour and the salt. Gently dredge each cake in the flour, patting it onto all sides of the cake.
In a heavy pan or skillet, over medium-high heat add enough vegetable oil to cover the bottom of the pan. Add 3 or 4 cakes at a time and cook for 2 to 3 minutes on each side, until the cakes are golden. Transfer the cakes to a rimmed baking sheet and bake for 10 to 15 minutes, until hot and a deeper golden color.