It is impossible to discuss the Internet Archive without addressing the copyright elephant in the room.
While the Internet Archive operates as a library, the uploading of full anime seasons sits in a legal grey area. Copyright holders (like Toei Animation and Crunchyroll) own the rights to distribution. dragonball z kai internet archive
Before searching the archives, it is important to understand why fans seek out this specific version. Dragon Ball Z Kai was created to celebrate the 20th anniversary of the DBZ anime. It is not a sequel or a remake in terms of animation style, but a restoration. It is impossible to discuss the Internet Archive
If you want to watch Dragon Ball Z Kai legally and safely: dragonball z kai internet archive