Hey,
Zbrush has become really slow when i’m moving my model around to work on ever since i did Ctrl+D, could this be because i subdivided it too many times? If so is there anyway of doing the opposite? (is that what the zremesher does?)
Thank you for any help! 
-Rachael
If you look under geometry you can “del lower” or “del higher” these are subdivision levels. If you want to optimize your topology you’ll need to use the zremesher or the topology tools and then use the “project” feature under the subtool menu to reproject the detail back onto your model.
Zremesher- http://docs.pixologic.com/user-guide/3d-modeling/topology/zremesher/
Project back detail- http://docs.pixologic.com/user-guide/3d-modeling/topology/zremesher/transferring-detail/
Zsphere topology- http://docs.pixologic.com/user-guide/3d-modeling/topology/zsphere-topology/
Topology brush- http://docs.pixologic.com/user-guide/3d-modeling/topology/topology-brush/
That’s all you’ll ever need to know.
Good luck.
Thanks Djordr!
Also check that you haven’t turned on Dynamic Subdivision (Tool>Geometry>Dynamic Subdiv>Dynamic) by mistake. Having that turned on while also having classic subdivisions really slows down ZBrush.
Cheers, i’ll check that to!