I'll just wash over this and say i loved Zant and even in girahim's wake, Zant still holds a very unique place in the Zelda franchise.
I know everyone has a problem with him going insane later on in the game but i can honestly say that this didn't bother or even surprise me, in fact i expected it.
Zant looks surreal, his costume, his helmet and the proportions of his body. Every time we see him we get a high pitched squeal from nowhere, yet during the cutscene following the Lakebed temple he has a deep sneering growl.. i assumed him to be making both of these noises and so his persona instantly felt cracked.
Zant also is seemingly very calm and collected throughout the game until the Twilight Palace, this again gave me reason to be wary of his mental state. He holds himself too still, he is too collected, he barely moves, even when he is attacking Midna. This just made me think that he was holding back, he seemed dangerous when he wasn't moving, and so i imagined him being even more dangerous should her begin to move. This notion came to be true when, in the Twilight Palace, he begins twisting his body, teleporting back and forth around the room which heralds his big battle against Link, which is a more impressive display of power compared to his earlier unmoving assault on Midna.
Again, from a cinematic point of view, the way Zant is framed and juxtaposed in shots within his scenes are also very unnatural. for example; during Zant's attack on Hyrule castle we first see him in numerous wide angle full body shots where we see him from a distance, but then the next shot is a very close framed close up of him, this isn't unheard of but it is rare (and not wholly used unless there is reason), as well as this, the shot is also canted giving a very unnatural sense of things, again coupled with the scream that accompanies his presence, Zant feels like one of the most surreal characters in Zelda's history. Surreal in the sense that he has and unnatural air about him and is far too collected, far too mysterious...
Perhaps i read too much into Twilight Princess as a whole but i do think its plot, narrative and characters are unfairly citicised for 'bad development and writing'. Midna also falls victim to the Zant effect, where people seem to perceive a change in Midna's personality as soon as she has adopted her true form, i also don't feel that this is true, much like i dont agree that Zant's insanity comes completely out of nowhere, i could go into much more detail but perhaps Zant is in need of a starring role within an article.