I think that this is beginning to move away from Rockbox questions and more into general computer usage.
It might be helpful to read up on cygwin and scripts; I've only got a tiny bit of knowledge myself, but I think Bagder has given you pretty much the entire script already.
Anyway, to answer your questions: yes, unsure, probably (but with the proviso that it'd be a better idea to call it something other than make zip in case you wanted to go back to the vanilla version).