Complex sentence: Dayyán was on his way to Baghdad to attain the presence of Bahá'u'lláh Who happened to be returning to Baghdad from Sulaymaniyah in Kurdistan.
Split into simpler sentences: Dayyán was on his way to attain the presence of Bahá'u'lláh in Baghdad. It was at this time Bahá'u'lláh was returning to Baghdad from Sulaymaniyah in Kurdistan.