(I updated the first post witht an abridged version of the following.)
Milestone #2: Zelda beats Mario on Switch alone.
My original prediction was that Super Mario Odyssey would be outsold by Breath of the Wild combined Wii U + Switch sales. Well now it doesn't even need Wii U sales to help it. Zelda just plain outsold Mario on the Switch alone. Currently, official Nintendo numbers has Zelda and Mario even at 17.41m, but they list Zelda above Mario on their "Top Selling Switch Titles" page. I suspect that Zelda is above Mario, but by less than 10,000 units, so they look the same after rounding.
I thought it would be useful to put Zelda quarterly totals here. There are a couple of times when sales are up YoY when compared to the previous quarter.
The Legend of Zelda: Breath of the Wild quarterly sales (in millions)
EDIT: Going to put Mario's sales here too.
Super Mario Odyssey quarterly sales (in millions)