Preheat the oven 200c/180c fan/Gas 6.
Line muffin tin with 16 muffin cases. You may need to cook in two batches if you don't have a big enough tin.
In a bowl combine the flour, baking powder, salt and cinnamon. Set aside.
In a separate bowl add the eggs, yoghurt, sugar, sweetener, oil, zest and juice of the lemon. Whisk together till fully incorporated and set aside.
Gradually fold the wet mixture into the flour mixture and add the grated carrot and courgette. Gently stir until combined. You do not want to over mix, only until the mixture has come together.
Now spoon the batter into the muffin cases and fill to the top, this will give a good sized muffins.
Pop into the oven and bake for 20 - 25 minutes or until golden brown. To check if they are cooked on the inside, slide a sharp knife in to the middle. If the knife comes out clean they are ready.
Allow the muffins to cool for 5 minutes before removing them from the tin.