Boil the potatoes, drain, cool then remove their skin.
Meanwhile, finely grate the courgette, season with salt and put the mixture in a sieve over a bowl. Rest for about 10 minutes.
Mash the potatoes roughly with a fork.
Using a spoon. push the liquid out of the courgette through the sieve then add the pulp to the potatoes. Add the minced garlic and lemon zest.
Thinly slice the spring onion, add to the potatoes, together with the flour. Season to taste.
Add some breadcrumbs and/or an egg and mix well – you should get a thick, sticky mixture.
Make about 6-8 balls, then flatten them into patties.
Scatter the breadcrumbs onto a sheet of parchment paper or a flat plate and coat the patties on both sides.
Heat some oil in a non-stick frying pan and fry the potato cakes on both sides until golden.
Transfer them to a plate, lined with paper kitchen towels, to drain.