why are icloud photos suddenly downloading as zip files

I have this problem too and have today been told by apple that it is a change in order to speed up the download process. I argued that it may well speed up the download process but we know have to go through a 6 step process just to get to the images in their raw state. 6 additional steps to view them how I did two weeks ago!

She advised I send feedback so, that if enough people did, it may get reversed but for now it is doing what it is supposed to do.

Please provide apple feedback and tell them you are unhappy.