Prove order is invariant under analytic isomorphisms.

Question

I have no idea where to even start this proof. Here is the theorem I have to prove:

Let $f$ be meromorphic on an open set $U$. Let $$\phi: V \rightarrow U$$ be an analytic isomorphism. Suppose $\phi(z_0) = w_0$, and $f$ has an order $n$ at $w_0$. Then, $f \circ \phi$ has order $n$ at $z_0$.

Answer 1

$\phi$ takes every value in a nbd of $w_0$ $n$ times.