Quote - took M5 apart in C4D.
M5 "just the skin" top gumm bottom ,gumm would Posable Symmerty.
teeth n eyes n all would not.never broke them in to peaceses to see if they would in peaceses
So All I know is somewhere between Daz Studio ,Genesis 1,Goz and zBrush.
There's a problem.not sure where.

 

I don't have M5, so I can't verify whether or not it is symmetrical after being exported from DS.

However, in regards to ZBrush, if a figure isn't perfectly symmetrical when you bring it in to ZBrush, you can use SmartResym to help. However, it's tricky when it comes to "unconnected" body parts that don't have a center seam that runs through the zero X coordinate.  This is why you can sometimes have difficulty with the eyes, teeth, etc of ANY figure that has had its symmetry shifted through various imports and exports.

You said the body symmetry can be fixed. The reason why is because it has a center seam that runs along the zero-X coordinate. Then it can compare the right and left sides of the model and adjust unsymmetrical vertices accordingly as best it can.

But the two eyes don't have a center seam; and the teeth don't have center seams. So ZBrush has no "center point" to reference. It has to take its best guess as to which points to match to which.

In order to determine where the problem is happening, you'll need to check the symmetry at each step. Make sure that the model is in its DEFAULT position (fully zeroed, no rotations, no translations, and no scales) before you export it from DS. Don't use GoZ ... just export it from DS as an OBJ file, and import that OBJ into ZBrush. Check the symmetry before you do anything else.