The Help panel that you're referring to applies to a Book file only and permits the zooming of the included files when opened from the Book. For individual document zoom controls, look at the lower-right corner of your Status Bar for the zoom contrrols.
See the following Help page: http://help.adobe.com/en_US/FrameMaker/10.0/Using/WS77BBA521-94BB-4980 -A086-835994532B81.html
Shortcuts for zooming in & out are:
In one zoom setting | Esc z i |
Out one zoom setting | Esc z o |
To fit page in window | Esc z p |
To fit window to page | Esc z w |
To fit window to text frame | Esc z f |
To 100 percent | Esc z z |
North America
Europe, Middle East and Africa
Asia Pacific