Although the Red Scarf Army began to gather people with Anbalism, its actual beliefs were mixed with Zoroastrianism. For example, Zhu Yuanzhang's branch belongs to Zoroastrianism.
The reason is easy to understand. The White Lotus Sect was originally a secret society mixed with Maitreya and Zoroastrianism, so it is natural for the Red Scarf Army to mix with Zoroastrianism.