In a colander set over a large bowl, toss together shredded zucchini and 1 teaspoon kosher salt. Let drain for 15 minutes, stirring occasionally.
Wrap the zucchini in a dish towel or cheesecloth and squeeze out as much liquid as possible.
In a large bowl, whisk together egg, thyme, garlic powder, pepper and remaining ½ teaspoon salt. Stir in zucchini and green onion. Gradually sprinkle in the flour, stirring until well combined.
In a large skillet, pour enough oil to a depth of ¼-inch. Heat the oil over medium heat. Line a rimmed baking sheet with paper towels and set aside.
Working in batches, drop zucchini mixture in heaping 3-tablespoon mounds in the hot oil. Gently flatten the mounds into ½-inch thick patties. Cook the zucchini fritters for about 2-3 minutes per side, or until golden brown and cooked through. Transfer to the prepared baking sheet. Repeat with remaining zucchini mixture.
To make the sauce, whisk together the sour cream and the red pepper jelly. Serve alongside the fritters.