Their entire first album is a collection of covers.
I assumed most people were aware of this.
(I have most of the original blues versions also. Always thought it would be neat to do a compilation of the originals in the same order as Zep I.)
It isn’t that the song is a cover, it is not credited to the author.
And while Page in the citation steers the discussion to riffs, the lyrics and title are the basis of the suit.
The drum beat from the intro to Little Richard’s “Keep a knockin” was used to lead into “Rock and Roll”. But that’s just a section of something (and Keep a knockin” wasn’t even Richard’s song, it’d been recorded by Louis Jordan in the 1940s and dated all the way back to the 1920s).