I'm going to assume that because there are secure actions involved, that you're going to need an add-on to accomplish what you want:

Code:
<Binding name="TOGGLEUI">
        if ( UIParent:IsShown() ) then
            securecall("CloseMenus");
            securecall("CloseAllWindows");
            UIParent:Hide();
            SetUIVisibility(false);
            ActionStatus_DisplayMessage(format(UI_HIDDEN, GetBindingText(GetBindingKey("TOGGLEUI"), "KEY_")))
        else
            UIParent:Show();
            SetUIVisibility(true);
        end
But even if you could create a macro solely for toggling the UI you would still need to bind it to a key for it to function...

So, why not just change the key binding from ALT+Z to something easier to press? Are you looking to save on computer resources by toggling off the UI?