I don't know about the Japan made ZR, but mine is a Korean made and it s_ux big time.
I don't deny it when dive bomb with out the stopper it feels smooth because of the ball bearing design, other than that it s_ux big time.

I think ZR trem(Korean) got to be redesign, 2 springs are just not enough and the saddles sux big time, the saddles got lots of sharp edges and when I install strings on it, it cuts my string it broke my strings alot when I do hard bending and pulling. I had to do alot of work on the saddles to curve and smoothen it so that it don't cut and break the strings. It happen even on the thicker gauges that I use. 0.09 was the worst 1 to use on that ZR, it broke almost instantly after tuning and bend it for the 1st time.

I own an Edge Pro and I think it's way much better and that's why it is still in Vai and Satch Signature series guitars.