Here a ZScript (v2) of one method to make transparent windows in a 3D object where the frames are one material and the windows another ... also you can see the backside frames.
There is one problem with it that material of the windows "overrides" the material of the back side frames cause of the 2.5D nature of ZB, However, since I thought this might be usefull to somebody ... I recorded the method.
Thanks to Andres, Veyes and Z2 for the help. (the ZSCR is actually the method Veyes' taught me ... sorry about shortening ur name Veyes ... I always shorten names cause its easier to type em )There is one mistake in the script where I adjusted the RGB/Z-Int while not in transform mode ... just igonre that part
The most intersting part was using double sided on the 1st instance.
hope it helps someone
Heres the ZScript ...