I tested part of this a while back 1) The power is doubled. I posted earlier in this thread regarding this, but it's a bit far back. 2) To get the double power, the move must move AFTER the other during that turn. So if a faster Zekrom uses Cross Thunder, then a slower Reshiram uses Cross Flame, Cross Flame gets double power. If Zekrom uses Cross Thunder on the next turn, however, it will not get a power boost (but Reshiram will if it uses Cross Flame). 3) I have not yet tested what would happen if there are multiple Cross Flames / Cross Thunders 4) These Pokemon do not have to hit each other to get the power boost. You can target both Cross Thunder/Flame anywhere and the one that moves after will always get the boost.