Grate the onion, carrot and zucchini and squeeze as much liquid out as possible (I placed the grated vegetables in a clean cloth to squeeze)
Place all the ingredients into a large mixing bowl and mix until just combined.
Divide the mixture into 6 and flatten to make burgers slightly bigger than your burger buns. (As they will shrink slightly when you cook)
Place an indent in the centre of each burger using your thumb. (This stops the burger from doming and shrinking)
Cook on a BBQ or place in a frying pan. Cook for 3/4 mins on one side (until the bottom is nicely browned. Flip and cook for a further 2/3 mins until cooked through.