Is it possible the Chinese domesticated the Przewalski's horse as far back as the 6th century?

Wikipedia:  Przewalski's horse has never been successfully domesticated and remains a truly wild animal today.

With its burning eye, flaring nostrils and prancing hoofs, this firey tempered charger becomes the legend of Chinese myths about celestial steeds that sweated blood and were really dragons in disguise. This is a reproduction of a 1500 year old paper and ink handscroll painting of the magnificent steed, Zhao Yebai, owned by Tang dynasty Emperor Xuanzong (6th century) painted by court artist Han Gan. The characters above the horse are a poem describing how King Mu rode this illustrious steed to Mount Kunlun to see the Queen Mother of the West at a location known as Turquoise Pond.  

"Is it possible the Chinese domesticated the Przewalski's horse as far back as the 6th century?"

The Przewalski's horse.

Przewalski's horse is stockily built in comparison to domesticated horses, with shorter legs. Typical height is about 13 hands (52 inches, 132 cm), length is about 2.1 m (6 ft 11 in). They weigh around 300 kilograms (660 lb). The coat is generally dun in color with pangaré features, varying from dark brown around the mane (which stands erect) to pale brown on the flanks and yellowish-white on the belly and around the muzzle. The tail is about 90 cm (35.43 in) long, with a longer dock and shorter hair than seen in domesticated horses. 

 The Przewalski's horse was described in 1881 by L. S. Poliakov. The taxonomic position of Przewalski's horse has always been problematic and no consensus exists whether it is a full species (Equus przewalskii), a subspecies of the wild horse (Equus ferus przewalskii), or even a sub-population of the horse (Equus ferus). Studies using DNA have been inconclusive, in part due to crossing domestic horses into the Przewalski's horse as well as the limited genetic variation present in the founder population of the Przewalski's horse. A 2009 molecular study using ancient DNA recovered from archaeological finds like bones and teeth places the Przewalski's horse in the middle of the domesticated horses, but more recent mitochondiral DNA analysis suggests that the Przewalski and the modern domestic horse diverged some 160,000 years ago.  The karyotype of the domestic horse differs from that of Przewalski’s horse by an extra chromosome pair either because of the fission of domestic horse chromosome 5 in Przewalski’s horse or fusion of Przewalski’s horse chromosomes 23 and 24 in the domestic horse. In comparison, the chromosomal differences between domestic horses and zebras include numerous translocations,  fusions, and inversions. Przewalski’s horse is known to have the highest diploid chromosome number among all equine species. Przewalski’s horse can interbreed with the domestic horse and produce fertile offspring (65 chromosomes).

The Mongol Horse


 The Mongol horse is the native horse breed of Mongolia. The breed is purported to be largely unchanged since the time of Genghis Khan.  Nomads living in the traditional Mongol fashion still hold more than 3 million animals, which outnumber the country's human population. Despite their small size, they are horses, not ponies.
Mongol horses are of a stocky build, with relatively short but strong legs and a large head. They range in size from 12 to 14 hands high and have a cannon diameter of about 8 inches. They have a certain resemblance to Przewalski's Horse.  Wikipedia

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