How do i get ZQuest 2.5.5?

I need zQuest 2.5.5. Where do i get it?

I think you are looking for ZC 2.55 alpha 1? That can be found here:
https://www.purezc.net/forums/index.php?showtopic=74455
ZQuest is a component of ZC, and is the editor. To play quests you need to run zelda.exe then after creating a savegame press the button assigned to "A" to bring up the menu to select a custom quest.