Joe Tedesco said:
Bend the cord over a finger and use a knife to
That is an excellent technique to use with zip cord. If you use a very sharp scalpel blade or even a very sharp, new, razor blade you don't even have to scribe.
Just lightly press the sharp edge against the point you want to strip and you'll see it literally split right under the edge, almost like butter. WOW!!!!
I think I tried that once with double-insulated cord but I split both the outside jacket and the inner insulators. Maybe I just was being a klutz.