Sorry if this sounds confusing because the interface is very busy, but try this: Go to gw2timer.com and navigate to the world map (there should be an option for that over on the right side. Then, in the upper right corner of the map pane, look for the Display option and click on it. Then enable Show zone gateways. Then you can zoom into the various maps and there will be a little swirly icon for where the zone boundaries are.
Hope that helps.
Incidentally, GW2Timer.com contains a wealth of information about the game, including when certain bosses spawn. However, it takes a while to understand everything you’re looking at.
Edit: I just noticed that the zone gateways don’t show up for Path of Fire zones, but it does lift the fog so you can see where the roads move into other zones.