The ZM was a "z" muscle design.  This moved more weight towards the center and deeper part of the club face.  The 710 MB is much closer to the 690 MB design.  The 710/690 is a more traditional muscle back where the center of gravity is a bit higher and slightly more towards the heel.  This provides for better feel on shots hit higher on the face (typical from the rough). Also, the weight distribution on a traditional design like the 690 and 710 allows for better shot control but may lack some added forgiveness the ZM provided.  

The new 710 sole design helps create better turf interaction for more solid feeling shots from a variety of lies.

I think it will best for you to get to a fitting account and work with the 710s.  Most players seem to prefer the feel of the 710 over the ZM.

I'm sure there are some TT members here that have made the switch and could comment on their preferences between the two.