Why can't the home screen rotate in Display Zoom mode on my 6 ?

Hello there, brichter!

Thanks for reaching out to the Apple Support Communities! It sounds like you are wanting to rotate the screen in Zoom mode on your iPhone. That is a great question. Check out this article here that talks about how to Use Display Zoom on your iPhone 6 and later. As you can see here:

With the Zoomed view on an iPhone 6 or iPhone 6s Plus, the Home screen doesn't rotate to landscape mode.

This is expected behavior that you are experiencing while using Display Zoom.

Cheers!