Different resolution and physical screen size between the two is why fewer apps appear with the zoom option on the 7.0 Plus. Drives me nuts since it's not accurate at all and doesn't provide the option for several apps I have that could have needed it
This makes some sense considering the Tab 10.1 & 8.9 resolutions are 1280x800 and the 7 is 1024x600.
Depending on what the density of the screen is on the Tab 7...it looks to be lumped in the
Large Screen, Medium Density category...take a look at the link below via Android Developers:
http://developer.android.com/guide/practices/screens_support.html#testing
There might be a way to lower the density to 120...maybe that will activate compatibility zoom. I'm not sure though if compatibility zoom is based on the
Extra Large Screen size or not.
EDIT:
Looks like most apps aren't utilizing this declaration in their Manifest...this attribute must be declared for tablets like the Tab 7 to utilize CZ. I think it's default for most tablets with a resolution equal to or greater than 1280x800.
http://developer.android.com/guide/topics/manifest/supports-screens-element.html#compatibleWidth
Also, there's no way to lower pixel density (facepalm). This is determined by the actually real estate of your screen and the resolution. We could lower it by decreasing resolution. That, basically, is compatibility zoom...it lowers your resolution to fit the size of your screen (lightbulb).