Download all icloud original photo at once

I have been an apple users since 2009 and now my cloud photo library is having almost 60,000 pictures, and would like to have a copy of the "Original" picture stored on an external hard disk. I know that we cannot download them at once which is also very hard process to do ?especially selecting the 1000 photo manually.

I have a nas drive but seems there is no integration between icloud and the nas.

Any suggestion how to download the "Orginal" pictures not the optimized in an easy way?