schematic symbol from power supply, two triangles pointing together
'Z' is often a designator for Transzorb, as is the symbol. However any SMPS I have ever seen normally use a 20mm MOV, which has a higher transient absorption rating. Confusing the issue even more is that 'Sidacs' use the same symbol, but are very expensive, often in the $20 to $40 price range.

Though I do not see values such as the rating of F1, this would be a low power circuit if only a Transzorb is being used.