You just elongate the vowel i.e. pronounce it longer. The double „ü“ just indicates this vowel to be stressed. Dialects do not follow a strict orthography, howe

You just elongate the vowel i.e. pronounce it longer. The double „ü“ just indicates this vowel to be stressed. Dialects do not follow a strict orthography, however, so you might find it written slightly differently in other contexts. Wirth lived in the United States for some time throughout his life but is a Zürich native. He must have spoken Züritüütsch („Zurich German“) privately, I am pretty sure (without having known him personally).