Scene is made of 4 separate elements linked between and placed in own layer.
Each model is Texture Unwrapped so any further texturing should not be a problem, metal parts and texture elements are separate mapped. You can see checker texture rendering and UWV mapping renderings how it looks like
Zipper_Slide (876 Quad Polys and 876 Vertecies)
Zipper_Teeth_Right (6160 Quad Polys and 6200 Vertecies)
Zipper_Teeth_Left (6160 Quad Polys and 6200 Vertecies)
Single Tooth is having 308 quad polygons and 310 vertecies
Zipper_Pull (456 Quad Polys and 454 Vertecies)
Zipper_Tape_Right (424 Quad Polys and 426 Vertecies)
Zipper_Tape_Left (424 Quad Polys and 426 Vertecies)
Each element is mapped separate and then at end all elements are scaled, in case you change scene you just need to move group of unwrapped mapping so they are not overlapping or repeating.
There are two materials in scene.
Metal (brass aged) 2K Textures Reflect, HGlossiness, RGlossiness same 2K texture Bump 2K texture in composite with noise procedural map