In a large mixing bowl, grate zucchini. Or grate in a food processor.
Grab a sieve, pick up the grated zucchini and place it in the sieve.
Over the same mixing bowl, drain the liquid from the zucchini by pressing it down into the sieve using a spatula, spoon, or your hands. NOTE: Depending on the type of zucchini will depend on how much liquid comes out.
Discard the liquid and place the zucchini back into the bowl.
Add the drained corn to the zucchini along with the spring onion, celery, parsley, garlic powder, and ground cumin, and season with salt and pepper. Mix with a wooden spoon well combined.
Stir through the egg.
Add the flour and mix until well combined, ensuring not to over-mix, just until all the flour is mixed through and you have a thick batter.
Add 2-3 tablespoons of oil in a large cast iron skillet or non-stick frying pan over medium-high heat.
Using your hands or a spoon, scoop up one heaping tablespoon of batter and place it into the skillet, pressing down with a spatula to flatten it into a thick disc. Repeat with 3-4 more fritters or what your skillet can hold, ensuring not to overcrowd the pan.
Cook over medium-high heat for 3-4 minutes on each side or until golden and slightly crispy. Adding more oil if needed into the pan.
Remove fritters from the pan and serve immediately, or if cooking in batches, keep the cooked fritters in a warm oven.
Enjoy warm fritters dolloped with sour cream or Greek yogurt!
Store leftover cooked fritters in a sealed container, refrigerated, for 3-4 days.