Before they are cooked, quinces are rock hard. They are perfectly easy to peel, but coring can be difficult and even dangerous. Recipes which blithely say 'peel and remove the cores' seem to ignore how difficult coring can be, One method is to put the quince on a workbench, place a piece of 18mm internal diameter copper pipe over the top of the core and bash the pipe through with a hammer (This is not recommended unless you are confident wielding a hammer, you cannot put the fruit in a vice as it will bruise)
J. McMoreland Hunter and S. Dunster, Quinces: growing and cooking (2014)
Elsewhere in the book, I am joyfully reminded that the judgement of Paris awarded a quince, not an apple.