Why do some fast bowlers struggle to pick wickets with red duke?
There have been some fast bowlers who are far more comfortable with the kookaburra ball and struggle using the red duke ball for Tests even though the fact that red duke helps fast bowlers more. In Ashes 2005 and Ashes 2009, I've read articles where Australian fast bowlers say that they don't understand the dynamics of red duke ball.
Zaheer Khan is one of the bowlers I know who is ineffective with Kookaburra but uses the red duke beautifully. Steyn is not as dangerous with red duke than with kookaburra.
Can someone explain me the dynamics of these 2 balls in brief?