Sorry for this auto-answer, but I'm still new to webpack and I just came across a possible solution.
Since kendo is referencing JSZip as global, you have to use ProvidePlugin as following:
config.plugins.push(new webpack.ProvidePlugin({
'JSZip': 'jszip',
'window.JSZip': 'jszip' // this doesn't expose JSZip property for window, but exposes it to every module
}));