I think original EQ had about 68 zones at launch, Kedge Keep, Solro Temple, Plane of Fear, Plane of Sky, Plane of Hate were all added piecemeal over the space of the following year before Kunark released.
But yeah a lot of the zones were divided due to limitations, think Freeport (3 zones), Neriak (3 zones), Qeynos (2 zones), Kaladim (2 zones), Erudin (2 zones), Felwithe (2 zones) Karana (4 zones) Desert of Ro (3 Zones), Commonlands (2 zones). Merge those and that's down to 54 zones, if we count Guk/Soldunga/b then we go down to 52. Arena is barely a zone so there is 51.
In terms of zone size we can probably guesstimate that if Pantheon reaches 40 zones it will be larger geographically than classic EQ at launch. When we look at the Thronefast streams we've been lucky enough to get some really wide overhead shots, and it looks like the equivalent of combining North Qeynos, South Qeynos and Qeynos Hills all into one giant zone.
We've seen multiple streams of Avendyr's Pass and it looks massive, there are large undead areas, orcish areas, human areas, a whole separate orc tribe to the north near what looks like Amberfaet. There is an outdoor mini dungeon for the bandits that they did. It could be an actual combined Karana equivalent, with more content density and less wasted space.
I guess as we see more streams we will see just how large some of these zones, especially the outdoor ones really are.
