Solution
= Solution
Write $p=p^*$, $\mu_z=\mathbb E(Y\mid Z=z)$, and $\tau^*=\mu_1-\mu_0$. The summand has finite variance, so the <central limit theorem> gives
$$
\sqrt n(\widetilde\tau-\tau^*)
\xrightarrow{d}N(0,V_{\mathrm{known}}),
$$
where
$$
V_{\mathrm{known}}
=\frac{\mathbb E(Y^2\mid Z=1)}p
+\frac{\mathbb E(Y^2\mid Z=0)}{1-p}
-(\mu_1-\mu_0)^2.
$$