Well Zelda Switch+Wii U is above MK8D, but for a single SKU we don't know yet there's no concrete number for both games other than monthly chart where MK8D Switch > Zelda BOTW Switch
Amazon is not really accurate indicator for a lot of games especially game on the platforms with good digital ratio, but for nintendo it's still relavant to see which game is selling better.
Zelda botw switch = 925k(1 month) switch hardware = 906k
MK8D = 550k(3 days) switch hardware = 1.18M
Mario Odyssey(3 days) = ??? switch hardware = over 2M
Amazon is estimate 10% of sales in the us. Its a good indicator thats it. Also switch botw is over mk8d sales