Dowloading from Google works for me with the default Z8 assets, but maybe not with old Zorro versions or when you have added other assets. If Google does not support the asset, the parse function returns 0 and the script crashes. Printing an error message instead is left as an exercise to the reader.

Google is no final solution since they will also discontinue the API some day. I'm afraid the final solution will possibly not be free.

-The Google download can be run before any script with Yahoo download. The script will detect that the data is already up to date. Google has also stocks, but major stocks are no problem anyway since you get them free from Quandl. The problem are ETFs.