Either Phantom Hourglass or Spirit Tracks. Both of the two are incredibly annoying and tedious. Honestly I didn't like them at all, and am still to this day wondering why they were published.
/shame
I'd have to skip AoL out of all of them. While I don't outright hate it, it is definitely my least favourite of the Zeldas and is frustrating to play because of the difficulty.
If we aren't counting Zelda I and II which I don't consider Zelda games really I'd probably pick Twilight Princess. Probably one of the worst Zelda games IMO and it's even a bigger let down since it's a 3D title. The only part I enjoyed about those games were the dungeons.
I'm shocked that people are saying games like WW, OoT and TP! those are the games i find myself replaying the most! My answer would be AoL. I'm struggling to get through it once and i can tell i will not want to play this again