Approach 1 : Get a copy of the CurrentSelection, which holds the item you selected. Invert it, so it contains the entire model except the actually selected item.
InwOpState10 myState = Autodesk.Navisworks.Api.ComApi.ComApiBridge.State;
mySelection = (InwOpSelection2)moState.ObjectFactory(Autodesk.Navisworks.Api.Interop.ComApi.nwEObjectType.eObjectType_nwOpSelection, null, null);
mySelection.SelectAll();
mySelection.SubtractContents(moState.CurrentSelection);
myState.set_SelectionHidden(moSelection, true);
Approach 2 :Create a InwOpSelection object, use the SelectAll method and then remove the selected item.
InwOpState10 myState = Autodesk.Navisworks.Api.ComApi.ComApiBridge;moSelection = (InwOpSelection2)
mySelection = (InwOpSelection) myState.ObjectFactory(Autodesk.Navisworks.Api.Interop.ComApi.nwEObjectType.eObjectType_nwOpSelection, null, null);
moSelection.SelectAll();
moSelection.SubtractContents(moState.CurrentSelection);
moState.set_SelectionHidden(moSelection, true);
And zoom the camera:
moState.ZoomInCurViewOnSel();
// or zoom on Selection containing the selected item
moState.ZoomInCurViewOnSel(mySelectedItemSelection);
Hope this works in plugins as well, I have written only one plugin to see if it works. And it was a long time ago, so I am not sure what API is available in plugins.