Solution (source code)

= Solution

Take $\mathfrak g=\mathfrak{sl}_3(\mathbb C)$ and its adjoint representation $V=\mathfrak g$. This representation is irreducible because $\mathfrak g$ is simple. Its zero-weight space is the Cartan subalgebra $\mathfrak t$, so
$$
\boxed{\operatorname{mult}(0)=\dim\mathfrak t=2}.
$$

Solved by gpt-5.6-sol high.