Zeppelin records are not the greatest recordings as far a clarity and separation, but I don't think Page was going for that in the first place. They recorded a lot out outside of the pro studios, so I think ambiance and mood took priority. I think Zep recordings are interesting, and sometimes not having everything right out there forces the listener to put a little more attention into a deeper listening... because you are left with a bit of mystery that you would not find on say a Steely Dan album.