I was thinking about this the other day, and the first example of "shredding" I could think of, was the 2:15 mark of Heartbreaker on Zep II.
A quick search on Wikipedia confirmed my hunch:
https://en.wikipedia.org/wiki/Shred_guitar
Zep II has never really been surpassed as "heavy" guitars record BTW.
Triple shit post incoming.
Kinda bluesy sounding, still. Shredding as an actual, intentional thing probably came around, what, 7-8 years after this album? Too revisionist to then run back and find the first precursor to actual shredding, IMO. If everything was invented and perfected by Zeppelin, rock was born and died in the 60's.
While I think Zep is certainly the greatest of the "heavy" bands of all time, plenty came after them- i.e., VH, Metallica, etc. They didn't everything. And you're right, Page hadn't fully left the blues behind here which I think you really need to do to be truly technically proficient shredding. But it's getting darn close right here. So maybe "proto shredding" is the better label, much like how "proto punk" laid the ground work for REAL "punk".
So is Eruption the birth of true shredding?[/b]