Hey Phil.....If it's a ZR trem and it's acting up a bit, that round thingy on the upper part of the trem (the area where your wrist rests, is an intonation tool. Unscrew that and use it to intonate. It's pretty simple actually. I've got a few Ibby's with ZR's. You shouldn't have to mess with springs at all if it's got the ZPS system in it (the roller wheel in the back). ZR's arent' actual "floating" trems perse, since they have back tension springs.
And maybe I'm speaking out of turn here....I haven't been over here for many moons...