For start, to get quince schnapps you need to smear hard fruits with resistant odors so that fermentation starts faster and lasts shorter. You must not put whole or insufficiently fragmented quinces. Pull out the pit, wooden parts and rotten parts if any. The wooden part starts to rot faster and it can spoil the schnapps, so be careful about that.
When you chop the fruit, add water with mixed baking yeast, it would be the best to have spring water or distillated water. If the fruit smash is too dense it will come to combustion while baking of schnapps. There are opinions that chopped fruits should be cooked for a little while before putting it for fermentation, but experiences have shown that that way you will get lower intensity of flavor, so it is up to you to decide whether to try it on that way or not.
Fermentation should last 13-22 days on 16-23°C. Fruit smash should be stirred everyday because carbon dioxide pushes pieces of fruit to the surface. Fermentation is done when the filtrate of cooked grinded fruits shows values of 6-12.
Generated schnapps should be overcooked because, unlike when you use plums, with quince you get a bit weaker schnapps. You can do overcooking right away or later.
From quince you can’t get large amount of schnapps, but quince schnapps is high quality schnapps with specific aroma. Of course, adding sugar can increase the amount of obtained quince schnapps, but you use on the quality.
The maximum amount of high quality schnapps from 100 kg of fruit you can get from without sugar is 8 liters max, and real quantity is 5-6 liters.
Quince schnapps should stay for 3-4 months in a glass bottles and after that period it gets is recognizable aroma.