Having used Choice Scarf Zekrom in the past, I found that one of the best moves to have on him was Volt Switch
, an invaluable tool for seizing momentum should Ferrothorn switch in (no iron barbs hurray), or you are unsure Kyogre will switch out but want to rack up damage, or just want the amazing benefits of such a scouting move. However, should Groudon switch in, Zekrom just stands there looking like a big bitch. Anyway, if you were going to change it for something I would replace either Outrage or Dragon Claw, whichever move you use less. There's pro's and cons to the whole "trading" moves thing, but the momentum-seizing thing is always fun against heavier stall teams.
TL:DR Part Two