I write songs and at times after a first draft and listen, I or my partner may notice it is similar to something. It's easy to change it up. I'm writing one now which sounded like Atlantis by Donovan to me and Ride Captain Ride by Blues Image to my co-writer.. after a bunch of tinkering melody/phrasing wise, I can't even imagine it to sound like either of them, although the chord structure is the same.

I wrote a lead lick in the 70's (which I have used in many forgotten songs I wrote) It just seems to be able to go with a lot of chords. I'm driving in my car listening to the radio in '87 and I HEAR MY fluffEN LICK BEING PLAYED BY R. E. M.! Cept at the end they go down in the melody from the eleventh note and shortened it up by four notes. The One I Love.
Now they never heard me playing it, it happens.

But this Led Zepplin / Spirit thing is uncanny.

Many times if I had writers block, I would read the chords to a big hit song classic, use their exact chords and then just speed it up, change the melody and BINGO! Another song. Everybody steals everything. There are certain chords that just go so well together, its natural to play them and so many are the same.

https://youtu.be/oOlDewpCfZQ