With Patch 10.1 available on the PTR now, we’re looking at the map of the new zone and where it’s located.
Zaralek Cavern is located between Ohn’ahran Plains and Thaldraszus. The location is highlighted on the map below.
Blizzard said the zone is slighly bigger than Shadowlands’ Korthia. Here’s the zone map of Zaralek Cavern.