I havent seen any research on ephedra with creatine, but I have seen that Caffeine cancels the creatine. And with ECA stacks you have lots of caffeine. Of course, you might still get benefit because rather than be dehydrated with caffeine the creatine makes you more "normal". Also, creatine doesnt just volumize your muscle cells, but also saturates your muscles with a pool of creatine for energy. SO that may also still be there.

Long story short: Caffeing reduces creatine effectiveness, but probably not all the way