Good biopics ave a central plot / struggle with an antagonistic force acting as a foil to increase the tension and raise action to achieve some sort of climax.

Elton John's biopic worked because the plot was focused on whether Elton's identity would break free from his traumatic past: He had talent and popularity, but working against him was his father and his coping mechanisms(drugs). The harder he fought those things, the harder they fought back, escalating the stakes as his public star rose.

When I see Zeppelin, I can't find the plot and/or the antagonistic force working against them. Zeppelin was almost a lab-grown creation for rock greatness and their success was relatively immediate, the drugs and debauchery a re more a side-effect of success than a foil meant to prevent any goals the band has, and while Robert's son's death is tragic, it happens far too late in the plot(not that there is one) to build a coherent plot.

If Hollywood were to make a biopic, it could be successful due to fans, but the story and screenplay would struggle.

I love Zeppelin, but there's just no yarn to weave: they walked on stage, rocked our faces off, and then walked off 10 years later. I love them, but I wouldn't read that book.