  We study the twisted ampleness criterion due to Collins, Jacob and Yau on
surfaces, which is equivalent to the existence of solutions to the deformed
Hermitian-Yang-Mills (dHYM) equation. When $X$ is a Weierstrass elliptic K3
surface, and $L$ is a line bundle and $\omega$ an ample class such that
$c_1(L)$ and $\omega$ both lie in the span of a section class and a fiber
class, we show that $L$ is always stable with respect to the Bridgeland
stability $\sigma_{\omega,0}$ provided $L$ has fiber degree 1 and $\omega
c_1(L)>0$. As a corollary, for such $L$ and $\omega$, whenever $L$ is twisted
ample with respect to $\omega$, or equivalently, $L$ admits a solution of the
dHYM equation, the line bundle $L$ is $\sigma_{\omega,0}$-stable, thus
answering a question by Collins and Yau for a class of examples.
