It is really hard to say with Zant and Midna since they always have something covering their ears, so we don't know if they are pointed or not. For what it's wort, the imp version of Midna has really pointy ears.
Prove to me that FS, FSA, ALttP, and TMC happens before TP...then I will back down from my theory about the Gerudo being the Twili.
Like I've said, I haven't played FSA so all I'm going by is what I've read on the internet. One thing that I have read about the Zuna though is that it says that the Zuna didn't really create the Trident of Power, but their ancestors did. These ancestors were skilled in magic but don't exactly have a name, but it seems logical that they may not actually be the Zuna, but just ancestors. The Gerudo, Twili, and Zuna could all be descendents of this 'dark magic tribe'.
This could explain why the Gerudo have close similarities to the Twili and the Zuna and also why the Twili and Zuna have similarities. Years ago they could have been a part of the same tribe that did create the Trident of Power. The trident could have been created long before anything in any of the Zelda games ever took place. I don't remember if the series ever touched on when the Master Sword was created, but it seems logical that the Trident of Power was created at the same time, as an opposition to the MasterSword.
Thus, I don't think the placement of the games matters as much. The Trident could been created by this ancient evil tribe that is unknown to us and then later evolved into three seperate tribes, the Gerudo, the Twili, and the Zuna. I really hope Nintendo sheds some more light on the subject. Perhaps if this is true, there are more branches of descendents that exist in the Zelda World that we have never heard of.