Fry the onion and garlic together in the oil till soft. Add the carrots to the pan and fry for 2 minutes add the zucchini, peppers and peas and continue to cook for a further 2 minutes. Transfer the mixture to a medium sized bowl and add the mashed potato, mint, lemon zest, crumbled feta cheese, beaten egg, 2 tablespoons breadcrumbs and season well with salt and pepper. Carefully mix together until the ingredients are well combined. Place the mixture in the fridge for at least 30 minutes to firm up. Remove the mixture from the fridge and mould the mixture into small patties using your hands. Roll the patties in the remaining breadcrumbs, covering all over. Next, heat a little oil in a large frying pan and shallow fry the vegetable patties for roughly 10 minutes, turning around once. When the patties are cooked, they should be golden brown in colour. Serve vegetable and feta cheese patties either hot or cold.