Your first piece of code doesn't do anything at all, because it just 
creates a class ZipUtils but does nothing with it (never instantiates 
it, never calls a class method).

Please make two complete standalone test programs to demonstrate your 
problem. This means that (a) we can see if we can duplicate your problem 
on our own machines, and (b) we can tell you why it's not working as you 
expect. Or you may find in the process of making these standalone 
problems where the issue lies.

It's also useful to know what version of ruby you're running under, and 
what O/S.
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