It has to be LZII for re-writing the landscape of heavy metal music.
LZI was/is great too, but after hearing the opening riff of Whole Lotta Love on a dash-mounted, one speaker AM radio (with Mom & little brothers), in our '62 Bel Air station wagon, nothing musically was the same.
For those of us with ears back then, we remember there was nothing like it to be found elsewhere and yes, it was played to death.
Got to hear the Houses of the Holy tour (7May-Jacksonville; go to setlist.fm) after the Zep had extensively rehearsed (see Rolling Stone , Greatest Concerts), and the arena quad speaker system was in it's glory. They opened with Rock and Roll and never looked back. On Dazed and Confused Page would "bow" his guitar and point it at which of the three upper speaker arrays he wanted the sound to come from. As I dimly recall, there were amazing pyrotechnics too (?).
I don't diss anyone's choices, but after a few of the songs on Houses I felt that they lost their pioneering, blues-based spark. Heavy drugs no doubt took their toll, not to mention the pressure to come up with new material, and don't forget, they were SUPER RICH. Hunger and desire, IMHO, makes a rock musician great!