I think the the rear drop vs. ZSP is somewhere between .5 and .75 inches - at least in our comparison. Hard to say for sure due to slightly larger tires on the BMW P car. It's more than 5mm though.
'07 e90 335i - SG/Black/Alum | 6 MT | Sport | Premium | Nav | CA
Dinan Stage 2 Tune, Stage 1 Suspension | BBS RS-GT