According to the Google Map documentation,
Android and iOS devices respect the following <meta>
tag:
<meta name="viewport" content="initial-scale=1.0, user-scalable=no" />
This setting specifies that the map should be displayed full-screen and should not be resizable by the user. Note that the iPhone's Safari browser requires this tag be included within the page's element.
Desktop computers do not respect the user-scalable
attribute, though mobiles will.
If you want to prevent zoom in Chrome on desktop computers, your best bet would be to enable kiosk mode with the following startup arguments:
chrome.exe --kiosk --incognito --disable-pinch --overscroll-history-navigation=0