Line a 15 x 10 x 1-inch baking pan with several layers of paper towels. Spread Zucchini (8 ounce) on paper towels and sprinkle with Salt (1/2 teaspoon). Top with another layer of paper towels and let stand for 15 minutes, pressing occasionally to release the excess moisture.
Meanwhile, for the lemon caper aioli, in a small bowl stir together the Mayonnaise (1/3 cup), 2 tablespoons Lemon (1) juice, Capers (1 tablespoon), Fresh Thyme (1 teaspoon) and Ground Black Pepper (1/8 teaspoon). Mix well and set aside.
Transfer zucchini to a large bowl. Add the Russet Potato (8 ounce) to the zucchini along with 1 teaspoon lemon zest, All-Purpose Flour (1/2 cup), Baking Powder (1/2 teaspoon), and Cayenne Pepper (1/8 teaspoon), and toss to mix well.
Add Egg (1) and stir until combined.
In a large nonstick skillet heat Olive Oil (2 tablespoon) over medium heat. Working in batches, drop batter by slightly rounded tablespoons into hot skillet. Use a spatula to flatten into patties. Cook 4 to 5 minutes per side or until golden brown, decreasing heat, if necessary.
Repeat with remaining batter, adding more oil as needed.
Serve fritters immediately with the lemon caper aioli.