"The country of Zhang Zhung was once a powerful kingdom that lay in what is now Western and Northern Tibet, centering around the famous Mount Kailash. As a written tradition, these teachings and practices are said to go back at least to the eighth century of our era, coming from the great Bonpo master Tapihritsa and transmitted to his disciple Gyerpung Nangzher Lodpo. The master Tapihritsa gave his disciple permission to set down in writing these precepts of Dzogchen in the Zhang Zhung language for the first time. Then in the tenth century, these same precepts were translated into the Tibetan language by Ponchen Tsanpo for the benefit of his Tibetan disciples. In the eleventh century, these precepts were collected from various sources in Western Tibet and in Nepal and put into their present form by Orgom Kundul and Yangton Sherab Gyaltsan. Thus, never having been concealed due to persecution, this transmission represents a continuous and uniterrupted lineage from the early times until present.
The chief disciple of the master Tapihritsa was the great Gyerpung Nangzher Lodpo. He was also born in Zhang-zhung, in the lake district of Darok in Northern Tibet. He began to study the Nine Ways of Bon became very proficient in all of these practices. Then at the age of forty-seven, he met Tsepung Dawa Gyaltsan who had previously been the master of Tapihritsa.
Five years after this first encounter, when Gyerpungpa was in retreat on the island in the Darok lake, at midday on the fifteenth day of the first month of summer, he had his second encounter with the master Tapihritsa which became known as "the Intermediate Advent and Encounter." The youthful Tapihritsa again appeared to him in a blaze of light, seated naked in the middle of a rainbow sphere suspended in the sky. Gyerpungpa prostrated to him and made three circumambulations. Thereupon Tapihritsa taught Gyerpungpa how to see in the ultimate sense, transmitting to his disciple the teachings regarding the Six Lamps.
Sometime later, Gyerpungpa had his third encounter with the master Tapihritsa while he was meditating again on an island in the Darok lake. Tapihritsa again manifested in front of him in his Nirmanakaya form. Tapihritsa then addressed him, saying, "You have been led to the Primordial Base. Now I will teach you the profound and secret oral instructions for Dzogchen. This will be my final teaching to you and it represents the highest teachings of Bon and the heart of the Tantra teaching. It is like the eye of the body." These teachings had originally come from the Dharmakaya Himself and had been transmitted by way of the celestial and the terrestrial lineages to Tapihritsa. The master gave his permission and at his command Gyerpungpa wrote down these brief teachings with blue ink on white paper. Thus he recorded "The Upadesha in Eight Chapters." Then Tapihritsa taught him "The Twenty-One Little Nails," which belonged to the exceeding secret cycle. This was their third and final encounter.
http://vajranatha.com/excerpts/dzogchen-in-zhang-zhung.html......detail from John Myrdhin Reynolds - Vajranatha
John Hopkins....Northern New Mexico