Zant is located in the Adventure Mode care of the grave gloves.
Once this is done you have the 3rd field from the left in the 3rd row. If you click on this you can see 2 rows of statues. Dig directly via the statue on the top left. After that you need to fulfill only the missions and you can use your Zant!
Agnetha is a character that you can unlock in Adventure mode.
The first thing you worried the water bomb and then go to the 7th field in the 4th row. There you have to destroy the stone there with the water bomb. If you have done this only have the missions to be done.
Then you can play Agnetha.
Unlockable Characters / Weapons Locations
Link Story Weapons: One-Hand, Magic Wand, Great Fairy, gloves (Morning Star), Master Sword
Zelda story Weapons: Rapier baton (from WW)
Impa Story weapon: Greatsword, Naginata
Sheik Story weapons: only the Lyra
Lana story Weapons: Deku Stick spellbook and ????
Darunia story Weapons: Only Hammer
Midna story Weapons: Only Bondage
Phai story Weapons: Only Sword of the Goddess
Ganondorf Story Weapons: Only broadswords
Now you in the adventure mode free Switches:
Zant: From left to right top 3 and 2 down. Then you get yourself a grave claw and links over the statue, complete the level and you did it.
Ghiharim: 2 links below to the right and 1 high then in the middle of the first bush where stands alone with the candle lighting, complete level. Ghiharim is now in your possession!
Agnetha: From the top (bottom center) 4 high and 1 right you complete a water bomb and throw it on the rock in the water level and you have the gold insect princess from Twilight Princess.
PS: (All weapons have not unlocked it in the story mode you have the adventure mode free games like for example the Great Fairy for Link or Zelda.
Blue hero costume: Collect the first image (Skulltulas Unlockable)
Red hero costume: Collect all 5 pictures (Skulltulas Unlockable)