@eggceptional - Just to set things clear here.
XYZmaker is 3D modeling software made by XYZPrinting.
XYZware is a slicer made by XYZPrinting so you can prepare your files for printing on daVinci machines.
Do you really want to edit your STL with XYZmaker?!
Anyway, in my experience with XYZware if you go with very complex STL's (usually size goes over 150MB) it struggles quite badly, beyond usability.
But to be honest nearly every other slicer have a hard time with these, even glorified S3D.
But doesn't seems it's struggling, it complains about unsupported format...
Have you tried to open any other STL with XYZmaker?! Have you tried to open that STL with any other viewer/slicer?!
Would be much easier if you'd upload that file so we could have a look. If you can't then that's ok.
I'd suggest you to get a free copy of Meshmixer. I use it to alter kind of a unprintable files or just make them better. Or in general it's packed with quite a lot of useful stuff.