Ocarina of Time sold 7.5 million on the N64, which was one third the end user base of the N64 and then sold 6 million on the 3DS so was certainly a success. Skyward Sword only sold about 4 million and it was released at the end of the Wii"s life cycle so had over 100 million players to sell to. Both Spirit Tracks and Phantom Hourglass both roughly a disappointing 3 million each on the DS. Zelda bounced back with the Switch and who knows where Nintendo will take the series.