You must have V4 already installed into your runtime first, the installers are not needed at all.  Now the WM zip content can be placed in any runtime of your choice, as long as all the zipped content are kept together.

For Poser, only the V4 Poser Installer is necessary; one belongs exclusively for DAZStudio (it has DS in the title) and the other is the powerloader which is also exclusive to DAZStudio.  V4 does not necessarily need to be in the main Poser runtime, but if you purchase additional morph packages in the future, they must be installed into the same place.