Step 1Trim the eggplant and zucchini and cut in half lengthwise. Arrange, cut side down, in steamer basket over simmering water in large pot. Steam the zucchini 3 minutes and transfer to paper towels to dry. Continue steaming the eggplant until it's very soft, about 20 minutes. Transfer to a colander and drain, cut side down, 20 minutes, until most of the liquid has seeped out.
Step 2Cut the zucchini into fine dice and place in a mixing bowl. Scoop out the eggplant pulp with a spoon and finely chop. Add to the zucchini.
Step 3Add the diced pepper, garlic, cheese, pine nuts, thyme and panko, and mix well. Season generously with salt and pepper. Stir in the egg and mix well.
Step 4Pour oil to a depth of one-fourth inch in a large skillet and heat until shimmering. Working in batches, shape the eggplant mixture into balls the size of small walnuts and roll in flour to coat lightly, shaking off the excess. (The balls will be soft but will take shape as they roll in the flour.) Lay the patties into the hot oil and cook until crisp and golden-brown, about 1 1/2 to 2 minutes on each side.
Step 5Drain well on paper towels and serve hot, warm or at room temperature, with hot sauce or freshly squeezed lemon juice if desired.