We have had user complaints around the zoom feature on Chrome M70+ on iOS. This is a feature request from katie@ to resolve this confusion:

It looks like users are often confusing in-page zoom with full-screen zoom. 

I wonder if we should disable page-level zooming when full-screen magnification is on? 

Then we could re-route ctrl-+ and ctrl-- and pinches to change the full-screen zoom level as long as full-screen magnification is enabled.