And can anybody give me a typ name for an 18 V zehner diode with 1.3 watt
1.3w is an unusual value, but you can substitute a higher wattage with no penalty (and a larger one might throw less heat depending on your application).
1N5355=18v 5w (but may not fit in a standard diode footprint)
5w is the next -common- size above 1w, but a small handfull of manufacturers make parts that are a closer match: