How to adapt layout for imac 27 retina?

Question

css

Faced with the problem of large displays, did layout for fullhd 1920 resolution and all mobile devices, but the customer has an imac 27 retina, everything on his display is very small, what is the way out of the situation? I have a smaller display (imac21 1920px) and I don't see the actual resolution the customer has. How can I adjust the layout to the maximum resolution? Is it possible to use zoom on the entire document model?
Link

Answer 1

Enlarge text with media query?
The coefficient is found out from a simple proportion, mathematics is about 5th grade.

Answer 2

Hmm set for resolutions greater than 1920 wide, the width is 1920px. done via meta viewport