The Legend of Zelda: Breath of the Wild will soon be the highest-selling Zelda game in the series.
Today, Nintendo announced that the Nintendo Switch version of Breath of the Wild has sold 6.7 million units globally. It was previously reported that the Wii U version has sold over 1.08 million units globally.
This brings total sales of Breath of the Wild to over 7.78 million units worldwide, making it the second-highest-selling Zelda game so far. (The highest selling game is, of course, The Legend of Zelda: Twilight Princess.)
Global sales for the entire Zelda series can be found here at the Game Design Gazette website