Complex sentence: In 1966 Atlantic signed a new reciprocal licensing deal with Polydor Records which, thanks to Polydor's recent distribution deal with Robert Stigwood's Reaction label, included newly formed British "supergroup" Cream, whose debut album was released on Atco in late 1966.
Split into simpler sentences: In 1966 Atlantic signed a new reciprocal licensing deal with Polydor Records. Thanks to Polydor's recent distribution deal with Robert Stigwood's Reaction label, the deal included newly formed British "supergroup" Cream, whose debut album was released on Atco in late 1966.