Zelda: Breath of the Wild has had phenomenal success in japan, and is now the second-highest-selling Zelda game in the country since Ocarina of Time, first released in 1998. The game has outsold all others in a short period of time.
Zelda: Breath of the Wild has sold 957,752 copies at retail, not including digital which would put it over 1 million. Furthermore, this is only on the Switch and does not include the Wii U sales numbers.
Ocarina of Time sold 1.25 million copies in Japan. Phantom Hourglass, sold 907,821 units and was the previous second best seller.
It is only a matter of time until the game overtakes Ocarina of Time.