Is the time series $\{Yt\}$ given by $Y_{t} = Z_{t} - \frac{1}{2}Z_{t-1}Z_{t-2}$
With $Z_{t} \sim{N}(0\,1)$, weakly stationary?
I do not know how to check if the above stated formula is stationary? I am struggling how to interpret the product of the same white noise time series with different lag?