I just answered this rather high-level ZeroMQ related question on SO and it occurred to me that it might be better on topic here, as there's really no code involved at this point. Though I think the OP was looking for a code tweak, and I asked him to rearchitect.
If you feel that a question is better on topic at another site then the best bet is to flag for a moderator at the original site. Just explain your reasoning why you feel it should be migrated.
Cross posting is generally seen as a bad thing unless the question is reworded enough to truly target the audience of the other site. Just be careful if you comment to the OP suggesting that it might be better on topic for another site.