Set grated zucchini in a colander and sprinkle with a few dashes of salt. Stir quickly, then let sit for 10 minutes. Grate the potato, then rinse shreds in another colander for several minutes, to reduce the starch. Squeeze excess water out of both.
Combine all ingredients in a medium sized bowl. Stir until well mixed.
Heat oil in a pan over medium heat. Once oil is hot, add dough by rounded scoops (about 2-3 tablespoonfuls) and gently flatten until about 1/2" to 3/4" thick. Fry for 3-4 minutes, then flip and cook an additional 3-4 minutes. Fritters should be golden brown on each side.
Transfer to a paper towel to cool. Serve immediately with a dollop of sour cream.
Store leftovers in the fridge. Fritters can be reheated, but do taste best when eaten immediately upon cooking.