Hi,
sorry for this late response.
Here https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcRsx7i6S0QzynAEEK6EIvl_opmtTw4mfAHcTQHte_XGUloDbfUdVQ you could find a photo of this zener diode soldered in parallel of the tantalum cap.
Tonight, when I get back home, I will check again what was the exact number of the diode and will post here it's data sheet.
Regards,
Erik