The myth of a sacred land hidden in glacial mountains and containing a sacred white lake or sea is said to have originated in the Altai Mountains of southern Siberia, after Indo-European nomads arrived there from the Russian steppes north of the Black Sea. Water was sacred to them, as was the color white, and the number 9 (3 x 3) was a sacred number. Some of these nomadic people eventually migrated south to form a civilization in the Central Asian desert, between Dunhuang and Khotan, others migrated to Iran. Zhang Zhung traded with the Altai and the desert oasis towns, and it's not unreasonable to assume that some of those northern people came to live in Zhang Zhung, which at one time did extend in territory to Khotan. A sharing of myth and tradition clearly took place. The "Tazik" (Indo-Iranian/Tajik) and Indo-European influence can be seen in the faces of Tibetan nomads today; genetically they are part Indo-Iranian/European, and part North Asian (Altaic). Archaeologists say there was a large migration of Iranians from the west into northern Tibet/Zhang Zhung around 500 AD, adding more Iranian influence to the Tibetan nomad genome.
The cosmology of Zhang Zhung does, indeed, share elements with North Asian cosmology, except that the Siberian peoples substitute a World Tree for the central mountain of Zhang Zhung beliefs. The trance traditions of Tibetan oracles are almost identical to those of Siberian shamans.