public static function div($z, $w) {
        if (!($z instanceof Complex)) $z = static::parse($z);
        if (!($w instanceof Complex)) $w = static::parse($w);

        $d = $w->x * $w->x + $w->y * $w->y;

        if ($d == 0) throw new DivisionByZeroException();

        return static::create(($z->x * $w->x + $z->y * $w->y)/$d, (-$z->x * $w->y + $z->y * $w->x)/$d);
    }