Zzp is the worst shift kit available. If you want a selectable firmness type thing, I hear good things about Intense. Transgo really is the best though.

There's always the DIY route where you order spacers from McMaster and put the in. The ZZP kit is just plastic spacers and you just put in a longer spacer for firmer shifts. Transgo has an entirely new spring set to put in. If Transgo doesn't fix your problem, no shift kit will.