To the best of my knowledge, Bobby Darin and Wayne Newton never performed together on stage, although Newton may have been an opening act for Darin very early in his career. The two were, however, hugely talented musicians. Both men played multiple instruments and had outstanding stage presence. Newton may have had the better singing voice (debatable), but Darin was a talented dancer, actor, impressionist (he did some impressions on Laugh-In) and song writer.
In his twenties, Bobby owned a record production company, TM Music/Trio, and signed Newton. When Bobby received the song Danke Schoen
, he decided that Newton’s voice was better suited for it and he gave it to Wayne. The rest is musical history and Danke Schoen became Newton’s signature song.