Place the mahi-mahi, dill, and green onions in a food processor and set on the medium speed until all ingredients are mixed together thoroughly.
Using the largest holes in a cowbell grater, grate the zucchini into a bowl.
Place the fish mixture into the same bowl and add the flour, breadcrumbs, horseradish, mayonnaise, pepper & salt and mix everything thoroughly.
Grease a large baking tray.
Take a palm-full of the mixture and form a patty about the size of your palm and at least a half inch thick and place on the greased baking tray about an inch apart. Repeat until all fish batter is used.
Spray or brush with olive oil and broil for 10 minutes. Then carefully remove from oven, flip the cakes and broil for another 5 minutes until golden brown.