I'm hopeful for a little advice, I'm half way through replacing the wheel hub assembly on my Z.  I'm as far as taking the brake disc off, and the 4 internal 17mm Bolts on the hub carrier.  BUT... for the life of me, I can't get the existing hub assembly out....  I've tried leverage, mallets, even  trying to force the two apart with a small chissel..to no avail.. 
  
Has anyone done this themselves, and if so any advice...and please don't say the existing hub assembly fell out....