Complex sentence: The librettist of the work is unknown: it may have been Picander, who had been providing libretti for Bach from at least the previous year when they collaborated on another academic cantata "Zerreißet, zersprenget, zertrümmert die Gruft", BWV 205.
Split into simpler sentences: The librettist of the work is unknown: it may have been Picander, who had been providing libretti for Bach from at least the previous year. They had collaborated on another academic cantata "Zerreißet, zersprenget, zertrümmert die Gruft", BWV 205.