The Zoroastrian religion is fairly cool but in our reality they practically got stomped by Islam and while they still exist they lost their status as a world religion, so how plausible is a Zoroastrian colony of Australia and how will it develop over the centuries, for example, how do they interact with the Aborigines, do they become a member of the Indian Ocean trade and how do they react to European expeditions in the area.
POD begins in 700