They did a chart somewhere with the different combinations and required levels to open up some of the advanced classes here, got to search in EE forums.
The class window will tell you the requirements in-game as well, no worries there.
Not all classes will be made available at launch as well, stated in the interview.
Didn't know about the Zumi name, since I usually play the foreign versions if they are accessible
No time to stick to a single game
Bonus: There will still be new classes added in future other than the ones you see above.
http://www.mmoculture.com/2011/05/ed...ss-teased.html