I tend to think that maybe Zaha simply wasn't 'match-fit' when he first arrived and only now he is beginning to show signs of being the player he was for Palarse
I think it doesn't really matter when he is used in the game, but would prefer him on from the start. That would enable us to 'get at' the opposition from the off and (hopefully) not bring him on when we are 1-0 down and on the back foot chasing the game (as has happened too many times this season)
He (Zaha) has had a hard time since coming to Cardiff City and it cannot have been easy for him. Since May last year, he has left his hometown club for the apparent bright lights of Manchester United, seeing his admirer-in-chief (Sir Alex Ferguson) leave, the new guy (Moyes) not fancy him, and a move to 'unfashionable' Cardiff City pretty much 'forced' upon him!
Only time (and there's not much of it left) will tell, but IMHO a partnership of Zaha and Whitts just might be the catalyst by which we avoid the drop this season, but it will take the rest of the team
AND THE FANS 
to join in the effort and give Cardiff City the momentum with which to stick two-fingers up to the doubters like Lawrenson and a few sad one from this Forum!