While I don't think it would be quite as quick and easy as all that, I agree it would be well within the capabilities of the EU or the US, and could be done at minimal cost in EU or US lives. The problem is keeping the peace afterwards. Bosnia initially had sixty thousand well armed troops. We'd need far more in the much larger Darfur. Where are we going to get them? In Bosnia we also had the convenience of fairly clear ethnic boundaries courtesy of the ethnic cleansing that had preceded the intervention. That made preventing reverse ethnic cleansing easier, unlike in Kosovo where most of the Serb minority was scattered among the Albanians.

we can't sort through centuries-old ethnic hatreds.

It's not centuries old ethnic hatreds that I'm worried about but rather quite understandable hatred generated by what has happened over the past several years.