Croatia and Kosovo both had the common enemy of Serbia; plus Rugova--the Catholic President of Kosovo--and the influential Albanian Catholic Bishop Marko Sopi of Kosovo both had ties in predominantly Catholic Croatia Croatia; they at times used Croatian based radio stations to broadcast into Kosovo. And going back a little further, both Slovenia and Croatia used the 1989-90 Serb revocation of Kosovar autonomy and imposition of rule from Belgrade as part of their rationale for seceding from the former Yugoslavia. So there were some connections.
And troops under Ceku's command were responsible for many atrocities against Serb civilians -- of course, our Islamofascist cheerleaders will tell you that there's nothing wrong with that.