Grate zucchinis using a box grater or food processor. Squeeze out excess moisture using a clean kitchen towel or cheesecloth to prevent soggy fritters.
In a large mixing bowl, combine grated zucchini, corn kernels, all-purpose flour, cornmeal, grated Parmesan cheese, baking powder, garlic powder, salt, and pepper. Crack in eggs and mix until thick batter forms.
Pour vegetable oil into a large skillet to about 1/4 inch depth. Heat over medium-high until shimmering but not smoking.
Scoop portions of batter into hot oil. Flatten slightly with spatula. Fry 3-4 minutes per side until golden brown and crispy. Work in batches to avoid overcrowding.
Remove fritters and place on paper towel-lined plate to drain excess oil. Keep warm in a low oven while frying remaining batter.
In a small bowl, mix sour cream, lime juice and zest, and chopped cilantro to make lime crema.
Serve fritters hot with lime crema on top or on the side. Enjoy as a snack, appetizer, or with fresh salad or grilled meats.