The larger part of the subject is not in India at all. Zoroastrians remained in Iran continuously, chiefly around Yazd and Kerman, through thirteen centuries as a barely tolerated minority: subject to the poll tax levied on non-Muslims, to periodic pressure to convert, to legal disabilities and at times to violence. The nineteenth century was particularly hard, and the emigration to India was its result. Parsi philanthropy from Bombay, organised through a society formed for the purpose, worked to relieve the position of the Iranian community and secured the abolition of the poll tax on them in 1882.
Present figures for Iran are usually given as fifteen to twenty-five thousand. The Islamic Republic recognises Zoroastrians as a protected religious minority with a reserved seat in parliament, and also maintains legal disabilities and a prohibition on conversion out of Islam that shapes what the community can do.
The counting is unusually unreliable, and one caution is worth recording specifically. Population series published for Iranis in India run into six figures and cannot be counts of Irani Zoroastrians, since they exceed the total Zoroastrian population of the country several times over. The word Irani in India also denotes a community of Iranian origin that is not Zoroastrian, and figures that do not distinguish the two are useless for this purpose.
What can be said is that the Irani Zoroastrians are a small community within a small community, that they are generally described as more open to conversion than the Bombay Parsi establishment, and that they share fully in the decline that is the defining feature of Zoroastrian life everywhere.