For the béchamel, melt butter in a pot. Stir in the flour and sauté lightly. Gradually stir in the milk. Simmer for about 5 minutes, stirring frequently. Add lemon zest to the béchamel and bring to the boil. Season with salt and pepper and put aside.
Drain for the chopped corn. Clean, wash and cut the leek into thin strips. Peel garlic and chop finely. Wash the chicken filet and pat dry. First cut in half horizontally, then crosswise into very fine strips and mix with starch.
Wash and clean the zucchini, cut in half lengthwise. Remove the flesh with a spoon, chop coarsely if necessary.
Heat the oil in a pan and fry the chicken over a high heat for 3-5 minutes, turning it over. Fry leek, corn and garlic for 2-3 minutes. Stir in zucchini meat. Season the shredded meat with salt and pepper.
Preheat oven (electric cooker: 200 °C/circulating air: 180 °C/gas: see manufacturer). Place the zucchini halves in an ovenproof dish (approx. 22 x 22 cm) with the cut surfaces facing upwards. Fill the zucchini with the shredded pieces. Pour béchamel over them and bake in a hot oven for about 20 minutes. Tastes good with rice, roast potatoes, bread or pure.