Actually it doesnt look impossile. Because in Viking Invasion of Europe, pagan Vikings learned Christian principles and many of them prefered to be Christian. Late Viking Invasion, they contacted with Almohads and Moors in Al Andulus Spain and Abbasid Caliphate in middle east. Also they connected with Byzantine Empire and they joined Byzantine army as mercenary soldiers. Some of them stayed in middle east and they blinded in Ortodox people. Perhaps some of them prefered to be Muslim, today for the historians it is possible. But for your topic we should imagine that these Muslim Vikings come back to their hometown in Scandinavia. An Islamic Baltic provides and Islamic north-east Europe. Because in Mongol Invasion, Golden Horde was established and it was a Muslim Empire in today's Russia and Poland, it means Scandinavia, Poland, Russia and Ukrain would be Muslim. It would be completely Muslim east Europe!!