Be careful with those regular expressions. In fact this will zip all files that have either ti or ep almost anywhere in their names. Your regular expression, /.tif?/ matches any character (.) followed by ti (ti) followed maybe by f (f?). This reduces to checking for ti anywhere except right at the start.

Maybe you are lucky and no unintended names matched, but you might want to take a look!

What you wanted is /\.tiff?$/ (.tif or .tiff at the end of the filename only -- adding support for .tiff since TIFF is the name of the file format, not TIF. Using .tif in the name is an unfortunate and obsolete legacy from CP/M.)

I notice you check for errors from writeToFileNamed, that's an excellent idea, often missing from quick single purpose scripts.