There are a number of approaches here- and though the position is that typically users should not be restricted when it comes to zooming for accessibility purposes, there may be incidences where is it required:
Render the page at the width of the device, dont scale:
<meta name="viewport" content="width=device-width, initial-scale=1.0">
Prevent scaling- and prevent the user from being able to zoom:
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no">
Removing all zooming, all scaling
<meta name="viewport" content="user-scalable=no, initial-scale=1, maximum-scale=1, minimum-scale=1, width=device-width, height=device-height, target-densitydpi=device-dpi" />