It took the Wii U about a year just to pass 4 million and that included 2 holiday shopping seasons. The crazy thing is these Switch numbers is the system still heavily supply constrained. If Nintendo can get enough systems ready by the holiday they'll easily surpass the Wii U's lifetime to date before it's even a year old.
Oh and Zelda is doing great as well. That 3.92 million for Zelda is only the Switch version so when you add the Wii U sales, the game is over 5 million. Of only 4 months it's already the 4th best selling Zelda in history and we haven't even gotten to the holiday season yet. The best selling Zelda is Twilight Princess with about 8.5 million so Breath of the Wild has a great chance of being able to surpass that. Hell, like I've said before, I think Breath of the Wild could be the first Zelda to hit the 10 million mark.