Answer
$x=\pm\frac12$
Work Step by Step
The zeros of the function are the $x$-intercepts of this function. The $x$-intercepts can be found by equating the function expression to $0$ and solving for $x$:
$$f(x)=-12x^2+3$$
$$-12x^2+3=0$$
$$-12x^2=-3$$
$$x^2=\frac14$$
$$x=\pm\sqrt{\frac14}=\pm\frac12$$