Most conservative approach? Lets make it easy:
TotK sold 2.24m units in Japan on its opening weekend.
It sold 10m units worldwide on its opening weekend (see Nintendo statement at that time)
So worldwide, it sold the 4,4 multiplied quantity of japanese numbers. If we do this same calculation now for EoW:
350k X 4,4 = 1.54m worldwide
OR (if Japanese numbers are a bit higher including digital)
375k X 4,4 = 1.65m worldwide
So this leads also to the number that I mentioned before. And if the game has a slightly underperformance in western markets, then the numbers will be even lower
@SkyerIst You do NOT consider in your assumptions, that EoW has a great overperformance in Japan, so you can not simply use the multiplicators of earlier Zelda games now. Example: TotK started 5x times better in Japan than in UK last year. EoW now started 6x times better in Japan than in UK, so the multiplicator has changed between Japan and European markets