As theme author, I don't have control over the link tag used for theme's style.css.
We use polyfills to support old IE browsers (11 and before), these polyfill scripts doe many things. For example, following scripts scan for link tags (type="text/css"), load over XHR, process CSS, and then update DOM.
These scripts are failing because origin changes when you are redirecting a relative URL to your CDN
/hc/theming_assets/1762844/2976249/style.css => https://p18.zdassets.com/hc/theming_assets/1762844/2976249/
- Add crossorigin="anonymous" or something if you are changing domain via server url rewrite
- Or, use proxy config on server instead url rewrite (this might not be scalable -- performance wise).