Line a large bowl with a kitchen towel. Wash zucchini and grate on the large side of a box grater. Transfer shredded zucchini to bowl with a generous sprinkle of salt. Let sit for 10 minutes.
Meanwhile, dice the red onion and finely chop green onions, mint, parsley, and dill. Set aside.
Using your hands, squeeze as much liquid out of the zucchini as possible. Then wrap in the towel and squeeze again, releasing as much liquid as possible.
Transfer zucchini to a large bowl along with the chopped onions and herbs. Add in the block of feta, using your hands to crumble. In a separate small bowl, beat the eggs then add in with the black pepper. Lastly, add 4 tbsp of flour and mix until completely combined. Do not over mix.
Heat 2 tbsp olive oil in a large pan over medium heat. Pick up a spoonful of the mixture and drop into the pan, repeat (do not overcrowd pan). Using the back of spoon, lightly press down to spread out into a patty shape.
Once the bottom side of the patty has crisped to golden-brown it's time to flip and cook the other side. Times vary but they generally need 2-4 minutes per side.
Work in batches and place on a paper towel lined plate to drain excess oil. Serve warm or room temp with tzatziki sauce!