I guess you didn't hear the French horn? Look, Led Zeppelin was great because they sounded unlike anything else of their time. Just like Chris Stapleton now. Then you find out that his big song was an old standard and he suddenly doesn't seem as great as you first thought. Now if all those LZ songs were theirs then everything changes.
I heard the French Horn, sounds like the opening soundtrack of an old spy movie I saw on television when I was a kid in the early/mid 60's....or maybe the french horn part was plagiarized from Led Zeppelin's Immigrant Song.
The two blasts of French Horn was six seconds in the three minute song.
Like I said, if you are looking for similarities you will hear them.
If you are not, they are completely different songs, the whole tune, the whole main guitar riff that drives The Immigrant Song right from the beginning, not the same at all.
Nothing I've ever heard about Led Zeppelin made them suddenly seem not as great, they were a great rock band, there is no dispute about that.
Obviously bits and pieces were stolen from various old blues tunes and transformed, and they covered some as well, and a few of the bits and pieces were big pieces.
Meanwhile, they wrote a bunch of really good music outside of the songs in question and delivered a number of the greatest rock records ever recorded.
It was pretty clear when I heard the first Led Zeppelin record, that they were another band that were huge blues fans, and later I learned that they were a bit liberal about borrowing lyrical phrases, as had been done in the blues for years, but that it mattered a whole lot more when they did it.
The Immigrant Song:
Inspired during their visit to Reykjavik Iceland in the summer of 1970, Robert Plant wrote his song about Vikings.
Six days after their visit to Iceland, Led Zeppelin first performed The Immigrant Song in concert at the Bath Festival 27–29 June 1970.
LF
recorded Ride the Sky in November 1970, the Led Zeppelin III album was released in the USA in November 1970.
How certain are you that LF did not plagiarize Led Zeppelin?...I don't believe either one was plagiarizing the other, but people believe what they want to believe.