Wash the quinces and apples and cut into pieces with the skin and seeds. Put both together in a large saucepan and add enough water to just cover the fruit. Then bring to the boil and cook until the fruits are soft.
Remove from heat, cover with a cloth and let stand for a few hours. Then pour into a large sieve and collect the liquid. Do not squeeze it out or the jelly will become cloudy.
Now stir in the sugar and bring the fruit juice to a boil, then let it simmer for another 2 minutes. Now you fill everything into the prepared jars, close them and turn them upside down for 10 minutes. In the case of jelly, you take 500 g of sugar per 750 ml of fruit juice
Another tip from me: I freeze the finished jam jars afterwards. This way the jam keeps its beautiful color and it tastes freshly cooked even after six months.