Sorry for my bad english…
I retopologized my character in Maya, how can I do to change the topology of my model in Zbrush?
Help me, thanks 
Nothing??
Export from maya as an obj file, in zbrush, go to your lower subd level, and import the mesh over it.
zBrush should ask “Do you want to project the details in the changed mesh”, yous hould press “OK”