My first search was "The top selling albums of all time". There were lots of results but not in 100% agreement. So to keep it simple, I asked Aria (an AI that comes with the Opera browser) the same question. I asked Aria again but included the words "worldwide sales" and the answer changed a bit - Zep lV, Bad and Abby Road no longer in top 10.
Thriller - Michael Jackson: 70 million copies
Back in Black - AC/DC: 50 million copies
The Dark Side of the Moon - Pink Floyd: 45 million copies
The Bodyguard (Soundtrack): 45 million copies
Their Greatest Hits (1971–1975) - Eagles: 42 million copies
Rumours - Fleetwood Mac: 40 million copies
Saturday Night Fever (Soundtrack): 40 million copies
The Wall - Pink Floyd: 30 million copies
Hotel California - Eagles: 26 million copies
Come On Over - Shania Twain: 20 million copies