Grate zucchini and toss it with 1 tsp. of salt in a large colander, let it sit for 30 min. The salt will draw water out of zucchini. Squeeze the zucchini to remove the excess water and wrap it in two sheets of paper towel, squeeze again. Don't skip this step! Place zucchini in a large bowl.
Chop the onion and saute in butter or oil over low heat for about 5 minutes. Add the onion to the bowl of zucchini along with feta cheese and dill, mix to combine.
Whisk flour and eggs together, the mixture will be sticky and add to the zucchini mixture. Combine all the ingredients together. At this point you can add more salt and freshly ground pepper. I didn't add any more salt because feta is already quite salty.
Your zucchini mixture will look more like a zucchini salad rather than a pancake batter,
Add enough oil to the large skillet to come up about 1/2 inch and allow it to get very hot. Drop the zucchini mixture the size of a golf ball into the hot oil and flatten it a bit to form a patty. Fry until golden on both sides.
Mix yogurt, minced garlic and chopped dill to make the garlic yogurt sauce. Serve immediately and enjoy!