It's already in Poser format, so just loading the PZ3 from within DS will get all of the mesh loaded, getting it to look even remotely similar however will be a total nightmare, DS can't read anything in a Poser material setting from the shaderTree line, so the few textures it can load from the P4 settings will make it look crap, basically you are looking at a total rebuild of every single surface setting using DS shaders.

Even using an .mtl or fbx or dae wont help, mtl has pretty much the same settings as the P4 materials, and fbx and dae importers in DS mean they aren't much better.