For the applesauce: Combine the apples, lemon zest, lemon juice, apple cider, 5-spice powder and sugar in a large saucepan over medium heat; stir to combine. Cook until the apples begin to break down but are still chunky, 10 to 15 minutes. Remove from the heat and let cool.
For the latkes: Grate the sweet potatoes and parsnips on a box grater and transfer to a large bowl. Season with salt and toss to combine. Add the flour and stir to distribute evenly. Add the eggs and stir well. Heat 2 tablespoons of the oil in a large saute pan over medium heat. Working in batches, form the potato mixture into 3-inch latkes that are about 1/2-inch thick. Add the latkes to the hot oil in a single layer and fry until golden brown on both sides and cooked through, about 4 minutes per side. Remove to a paper towel-lined plate and season with salt. Repeat the frying, adding more fat as necessary.
Serve the latkes with the applesauce, sour cream and scallions.