Wash the zucchini and cut off the ends. Mix with the lemon juice and mix into small pieces.
Add the preserving sugar, stir well and cook for 4 minutes (follow the cooking instructions on the preserving sugar package). Pour into prepared twist-off jars and close.
If you like, you can add dried and finely pounded mint leaves (I usually use 2 teaspoons) to the zucchini-lemon mixture and bring everything to the boil.