$2+i$ and $i$
Work Step by Step
The Conjugate Pairs Theorem says that if a polynomial has real coefficients, then any complex zeros occur in conjugate pairs. That is, if $a + bi$ is a zero then so is $a – bi$ and vice-versa. Its degree is $4$, hence it has $4$ complex (including real) zeros. $2$ zeros are already given, hence there are only $2$ zeros left which are $2+i$ and $i$ (the conjugates of $2-i$ and $-i$, respectively) according to the Conjugate Pairs Theorem.