Then put them in a saucepan with boiling salted water and boil for about 10-15 minutes, until tender.
Drain the zucchini and puree them in a blender. Transfer them to a strainer and squeeze with our hands to drain their liquids.
Put the zucchini in a bowl, add the onion, kefalotiri, powdered melba toast, eggs, salt and pepper to taste and knead to combine. Cover the bowl with plastic wrap and leave it in the fridge for 1 hour, for the flavors to combine and the mixture to stiffen.
Now, it is time to make the "kolokithokeftedes:: We slightly wet our hands; take pieces of the mixture and shape into small, golf like balls. Gently press with our palms, to flatten them a bit and coat them with powdered melba toast.
In a deep frying pan heat plenty of olive oil, and when hot, fry the "kolokithokeftedes", in small batches, turning on each side, until evenly golden-brown
Remove with a slotted spoon and drain on paper towel. Repeat with the remaining ones.
Serve the "kolokithokeftedes" garnished with basil leaves.