i made my base mesh in blender, imported it into zbrush for sculpting… and it wont let me mirrior my brush over the z axis. (i have to because of how blender exports the mesh) i can mirror over the x axis still, but not the z or y.
It’s kind of hard to answer that without being able to see the model. But the most likely possibility is axial switching. For example, what’s the Z axis in one app might be the Y axis in ZBrush. If that proves to be what’s happening, you could look at the ImportExport Options in the Preferences palette. There are settings there to switch axes upon import and export.