The first Zoroastrians became Bahá'ís, in Persia. [SBBH2:67; RoB3p268]
For information on these converts see SBBR2:67–93.
The revelation of Lawh-i-Haft Pursish (Tablet of Seven Questions) (Date unknown) in answer to the questions put to Bahá'u'lláh by Ustád Javán-Mard, the Secretary of the Council of Zoroastrians of Yazd. [RoB3p272]