Put the zucchini and onion in the centre of a clean tea towel, gather corners together and twist as tightly as possible to remove all the juices. Combine the zucchini, onion, flour, cheese, mint, parsley, nutmeg, breadcrumbs and egg in a large bowl. Season with sea salt and freshly ground black pepper, then mix with your hands to a stiff mixture that clumps together.
Heat the oil in a large frying pan over a medium heat. When hot, drop tablespoons of mixture into the pan and shallow fry for 2-3 minutes, or until well browned all over.
Drain well on crumpled paper towels and serve hot with lemon wedges or tsatsiki.