Zopf is something between challah and brioche, main difference, it's less enriched or sweet, and it's from Switzerland. Sundays were the days we'd enjoy zopf at my sisters along with gipfeli (croissant). Generally it's a yeasted loaf and so I had the notion of making it with a sweet sourdough, and I'm pleased to say it worked! Just add some jam, butter and your fine.