Players say the portal from Stormwind's Mage Tower to the Dalaran Sky boat became one way near the end of the beta, so it won't take you back to Zephras Isle. To return as Alliance, one player says you travel through Southshore, walk to Dalaran and take the flying boat from there. This comes from a player thread, and we haven't confirmed the route on live.
Going the other way
If you're on the isle and want to reach Elwynn Forest, check your hearthstone first. If it's still set to the isle, set it at an inn in Goldshire or Stormwind once you get there.
What's confirmed
Blizzard's development notes list fixes to Zephras Isle quests such as "Catching Wind" and "A Firm Response". They don't describe the travel routes.
Skyborne quests not showing
Some players who bought a pack for the Skyborne race report no quests appearing for their new character, while other races see quests straight away. Unverified, with no staff reply when we checked. Try a relog and clear your map filters. If that doesn't help, report it on the bug forum.
More on the race in our Skyborne guide.