The Zoroastrian cosmology, as expounded in the Bundahisn and other Pahlavi works, encapsulates Zoroastrian belief about God (Ahura Mazda), the world, human nature, and destiny.
Zoroastrian ethics are founded on this understanding of cosmogony. By nature men and women are perfect, free of all suffering, and sinless. As evil is in essence destructive, it is humanity's duty to expand the Good Creation both through expanding the world (e.g. in farming), and by having children. It is a religious obligation to enjoy the Good Creation, and to refrain from despoiling or abusing it.
"Bundahisn." The Concise Oxford Dictionary of World Religions. . Encyclopedia.com. (August 16, 2018). http://www.encyclopedia.com/religion/dictionaries-thesauruses-pictures-and-press-releases/bundahisn
"Bundahisn." The Concise Oxford Dictionary of World Religions. . Retrieved August 16, 2018 from Encyclopedia.com: http://www.encyclopedia.com/religion/dictionaries-thesauruses-pictures-and-press-releases/bundahisn