I had a single model in ZBrush with multiple levels of divisions. I applied an arbitrary UV map on this single model, and exported low and high res versions. I'm not sure how else to match UV maps. Prior to doing this, I received an error message informing me that said UV maps needed to match. After the ZBrush export, that error did not appear. I guess I assumed that I had taken care of the UV problem, but perhaps not.
Thank you cakeller for your help! However, 3DCoat already doesn't like importing these high res meshes as a 'big mesh' much less anything else. I usually get a memory fault. This is understandable, seeing as these meshes are over 5 million polygons each (sometimes up to 10 million). In other words, even without subdivisions or smoothing, I could not get the large high-res mesh to import.
However, I went into ZBrush, exported a level 1 'reference mesh' and decided to do the retopo-ing on these. This way I get a mesh around the right shape. I then take it into XNormal to export out my normal maps between this new retopo model and the high-res model, as I need to get these done ASAP for a job. I'll then paint the low res retopo model and export that map from 3D Coat. It's not a great workflow, but at least it is getting my work done.
Ha, my pipeline has many kinks in it...
I appreciate the help and will continue to look into this after this particular job is done.