 Curvature bispectrum from a zeta zeta-prime-squared interaction

For $H_{\mathrm{int}}=-M_{\mathrm{Pl}}^2\int d^{3}x{a}^3{ϵ}^2\zeta {\dot{\zeta }}^2$ and the standard Gaussian de Sitter modes, the tree in-in formalism gives $B=H^4{\sum }_{\mathrm{cyc}}{k}_2^2{k}_3^2(K^{-1}+k_1{K}^{-2})/[16ϵM_{\mathrm{Pl}}^4(k_1{k}_2{k}_3{)}^3]$, where $K={\sum }_i{k}_i$. The result includes six connected Wick contractions and a vacuum contour.