Combine water, agave nectar, white sugar, and orange juice in a saucepan over medium-high heat and bring to a boil.
Meanwhile, wash and peel the quince fruits and cut out any dark spots. Add whole quinces to the boiling liquid and reduce heat. Simmer for 10 minutes. Turn quince over 180 degrees and simmer an additional 10 minutes. Add cranberries and simmer until quince are tender to a knife, 10 minutes.
Serve quince cored or whole with the cranberries and syrup ladled over them. Top with orange zest.