Probably the most famous Zbigniew outside of Poland is Zbigniew Brzezinski, who was the National Security advisor to the US president Jimmy Carter in the 1970's.
Other less common forms of this name (other than Zbyszek) are: Zbyszko [ZBY-shkoh] (medieval sounding, because it ends in -ko), Zbych [ZBYH] and Zbychu [ZBY-who].