From searching forums, and looking at concert pictures, it seems that Zeppelin use the Shure SM57 equivalent of the day, the Shure 545 Unidyne III. I believe Robert used one for vocals, and Jimmy and Jones likely used them as cab mics at times. I still need to dig into more pictures to see when and where they used them, and how they mic'd their cabs generally.
I found a good deal on a vintage 545, pics to be added.
TODO: Add pics.
TODO: Go through the LedZepNews gear loadout list and see what mics Showco has listed.