I haven't had a chance to play a serious 4e or e6 game... but I don't think both would work...
Please remember that the
point of E6 is to stop leveling up after you reach 6th level. It creates a stable environment at a fairly low level where there's less of a struggle of power between the PCs and the monsters. E6 doesn't do anything drastic to change the rules of the game.
That's it. You stop leveling up at 6th level. It's gotta be the easiest D&D variant
ever.