Like Equation 9 for the first stage moderation model, Equation 19 indicates that the first stage of the indirect effect of X on Y varies as a function of Z, as captured by the term (aX5aXZ5Z)bM6. However, Equation 19 shows that the direct effect of X on Y also depends on Z, due to the term (bX6bXZ6 Z). The intercept in Equation 19 is also affected by Z, as reflected by the terms bZ6Z and a Z5 Z.