Cut the potatoes in half, then into quarters and slice.
Add oil to a 9-10-inch (23-26 cm) non-stick frying pan over medium heat. The oil is ready when you drop a piece of potato in and it sizzles (you don’ want it too hot). Add the potatoes and onion. Cook without browning, for a couple of minutes, then the add bell pepper and cook for another 5 minutes. Add the zucchini and continue to cook, stirring often so they all cook evenly until the potato is tender when pierced with a fork. Add a colander over a pan or large bowl and drain them.
Add the eggs and vegetables to a large bowl and mix well.
Add 2 tablespoons of the drained oil back into the same pan and return to medium heat. When the oil is hot, carefully pour the egg/potato mix into the pan and smooth into an even layer. Cover with a lid, this will help it cook faster. Cook for, 10-15 minutes until the bottom is browned and starts to set. Once the edges start to set, I like to use a rubber spatula to carefully lift it a little to make sure it is not getting too brown on the bottom. If it is, turn down the heat slightly.
Once the top has started to set (but still a little liquid in the center), place a plate over the pan, that is larger. Carefully, but quickly, flip the omelette onto the plate, then slide back into the pan. Use your spatula to reshape if it got a little messy. Replace the lid and cook for a further 5-6 minutes if you like the center set. Cook less if you like the center soft.
Slide out into a board and allow to cool slightly before cutting and serving.