I haven't used a ZR trem, but I thought my experiences might be helpful:
I use an Ibanez RG470F/TBL with a licenced FR trem. I've dropped the tuning down to A-E-A-D-F#-B by increasing the string gauges to 56-46-36-26-18-13 (I think - the strings I use are D'Addario EJ22s). The tension is about the same as standard tuning with gauge 10 strings, more or less. I had to do a bit of adjustment to get it just right, but nothing too difficult :)
Not sure if this helps, but I hope it does!
Roo