That r_fletch_r script is probably the best way to resize, but the Transform Toolbox is similar, and already built into Max (at least since 2010?). Here is a small sphere of random size that made match the 64 unit cube.
r_fletch_r's script is pretty cool. Personally in the past I have just used a 2x2 FFD cage for this type of thing. You can just select the verts from the top, bottom, or whatever and numerically align them to the grid or to a specific position on whatever axis.
To my knowledge zbrush only changes the scale of the mesh if you scale it with transpose, use the size deformation, or change the import/export values. Otherwise it spits out the same obj that went into it. I did have Roadkill shrink my latest character though. I'm in another program, but to fix it I just used a script…
I don't use zbrush as much anymore, but to my knowledge zbrush also has historically done this when you hide part of your mesh and save with multiple subtools. There's usually a way to counterscale it in the Export settings from zbrush. - other subtools are rescaled based on the size of the base subtool... or hte other way…