Trim and roughly chop the leeks and zucchini and place in a large pan on low heat with the thyme and a goodly sized splash or two of the oil.
Cook gently for 30 minutes or until soft and lightly golden.
Add a little salt and pepper to taste and allow to cool 5-10 minutes.
Preheat the oven to 180 Centigrade (350 fahrenheit).
In a separate bowl flake the salmon, crumble in the feta, grate in the zest from the lemon ,crack in the eggs and stir to combine.
Stir them into the vegetable mixture.
Layer the filo over the base of an ovenproof frying pan or dish (about 30 cm), overlapping the sheets and letting them hang over the sides Lightly brush teh sheets with oil as you go. Make sure that you fully cover the base and allow enough overhang to fully cover the filling when you fold it in later.
Spoon in the filling then fold in the overlapping filo to form a lid.
Brush the top with olive oil.
Bake on the bottom shelf of the oven 45-50 minutes or until cooked through and golden and crisp.