Zoroastrianism and Vedic thought share a common root in ancient Indo-Iranian religion, and as such, there are many similarities between the two belief systems. One of the most significant areas where Zoroastrianism had an impact on Vedic society is in its social structure.

The Vedic society was divided into four varnas or social classes - Brahmins, Kshatriyas, Vaishyas, and Shudras. This division was based on one's occupation and was considered a fundamental aspect of Vedic society. However, Zoroastrianism brought a new concept of social hierarchy, which was based on one's moral character rather than their occupation.

In Zoroastrianism, there are three classes - priests, warriors, and commoners. The priests were considered the most important class as they were responsible for upholding the teachings of the religion and performing rituals. Warriors were seen as protectors of the community, and commoners were expected to follow the teachings of the priests and contribute to the community's well-being. This hierarchical structure was based on one's moral worth, rather than their occupation, and it influenced the Vedic society to a great extent.

Zoroastrianism also introduced the concept of duality, with the belief in a constant struggle between good and evil. This idea of moral duality had a significant impact on the Vedic society's social structure. The Brahmins, who were traditionally seen as the highest class, now had a moral responsibility to uphold the teachings of the religion and maintain the balance between good and evil. This elevated their status and gave them a more prominent role in society.

Additionally, Zoroastrianism's emphasis on individual responsibility and accountability also had a significant impact on the Vedic society's social structure. In Vedic society, one's social class was determined by birth, and there was little room for social mobility. However, Zoroastrianism taught that one's actions and moral character determined their place in society, rather than their birth. This idea challenged the rigid social hierarchy of the Vedic society and gave individuals the opportunity to rise in social status through their own efforts.

In conclusion, Zoroastrianism had a significant impact on the social structure of Vedic society. It introduced a new concept of social hierarchy based on moral worth, rather than occupation, and emphasized individual responsibility and accountability. These ideas challenged the traditional social structure of the Vedic society and influenced it to become more flexible and inclusive.