I still am NOT the guy to ask about MFC, but http://msdn.microsoft.com/en-us/library/5k9f064x(VS.80).aspx suggests that you can get your main CWinApp object using the AfxGetApp() function. It would be a matter of dynamically casting it to type ZWinApp:
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ZWinApp *app = dynamic_cast<ZWinApp*>(::AfxGetApp());
//If the cast fails, the pointer is NULL.
if (app)
{
//Good. Call whatever member you need:
app-><The member name>;
}