Thats quite a jump for GoW, not sure why that optimistic about it. Its possible i dont see it. Hell doing 8mil is already crazy and impressive as it is.
With that said im expecting higher for Zelda than 10mil anyway. Thats the floor in sales at this point. BotW for switch is probably at pr close to 7mil already and the game is still charting everywhere despite being a year old (even in the UK it was at number 5 last week)