Buddha eminated as Garab Dorje turned the wheel of Dzogchen teaching

What is the connection between Buddha Shakyamuni’s teachings and Dzogpa Chenpo. Buddha often taught Vajrayana teachings in different forms. Not in a bikkhu’s form, but in a deity’s form, like Kalachakra, [for example]. when He taught Kalachakra’s teaching He was not wearing a monk’s robe, but he eminated as Kalachakra. In the case [of Dzogchen teaching], many teachings, many texts say that. Garab Dorje was emanation of Buddha Shakyamuni and Vajrasattva. And He turned the wheel of Dzogchen teaching.

Hungkar Dorje Rinpoche, “Introduction to Longchen Nyingthik (Part I)”