Solution
= Solution
Put $b=1-R>0$ and $m_b=\mathbb EX_0^b$. Homogeneity of the <constant relative risk aversion utility> gives $U(z_N)=U(z_n)\prod_{j=n}^{N-1}X_j^b$. Thus
$$
\boxed{\mathbb E[U(z_N)\mid z_n]=U(z_n)m_b^{N-n}.}
$$
As before this is an extended-valued <conditional expectation> if the required moment is infinite and days remain.