In a medium bowl, combine sour cream, kosher salt, black pepper, garlic salt, and cayenne pepper. Stir well, then refrigerate while you prepare the fritters.

Grate zucchini into a clean kitchen towel or cheesecloth. Sprinkle lightly with a pinch of kosher salt and let sit for 10 minutes to draw out moisture. After resting, squeeze out as much liquid as possible over the sink. Set aside.

Grate onion into a small bowl and drain thoroughly using another towel or paper towel. You want to avoid adding excess moisture to the batter.

In a large mixing bowl, combine drained zucchini, drained onion, corn, garlic, mozzarella cheese, eggs, flour, kosher salt, black pepper, and baking powder. Stir until everything is evenly mixed and a thick batter forms.

Heat olive oil in a large nonstick skillet over medium heat until shimmering.

Using a 3-tablespoon scoop, portion the batter into the skillet, flattening each one into a round about 3 inches wide. Cook in batches, making sure not to overcrowd the pan.

Cook each fritter for 4 to 5 minutes per side, or until deeply golden brown and cooked through. Adjust the heat as needed to prevent burning or undercooking.

Serve warm with the dipping sauce on the side.