Let $p(x)$ be a polynomial of degree $n$ with only even powers. That is, $$p(x) = \sum_{i \text{ even}}^n c_i x^i$$
I am wondering if we can say anything about the properties of the zeros of $p(x)$, other than if $z$ is a zero then $-z$ must also be a zero. (Assume in general that $c_i \in \mathbb{C}$ but if $c_i \in \mathbb{R}$ that is fine too.)
Or if $p(x)$ can be factored into some nice form.