The title really says it all. There's no measurements because all Zippos are not created equal.
Step 1: Materials/Tools
-Cardboard (I got mine from my webcam package)
Step 2: Trim
Trim down the edges of the cardboard so that there is nothing hanging off.
Step 3: Trace and Cut
Trace out all your sides just a bit bigger than than the actual lighter.
Then cut out the sides and cut the sides, front, and back about a quarter inch short.
Step 4: Placement
Put the pieces of cardboard on a strip of duct tape like shown in the picture.
Next fold the duct tape around the cardboard. (Picture 2)
Place the bottom piece of cardboard on a strip of duct tape, and and wrap it around.
Step 5: Test
Put the Zippo into the holster to make sure it fits right if its a bit to tight just stretch it a bit.
Get one last piece of cardboard for the belt loop.
Wrap it in duct tape and trim off any overlap.
Place it on a strip of duct tape.
Place one end of that strip into the holster and use the lighter to press it into place.
Wrap the rest of the duct tape around the bottom.
Step 7: Done
Now your finished. Put it on your belt and try it out.