What do bending moments look like after coordinate frame rotation?

Suppose a 3D body had certain bending moments about the x, y, and z axes. What would the bending moments about a different coordinate system look like? In my case, I have restricted myself to a planar rotation.

Here’s what I thought might work.

Let’s $M_z$ be the moment about the z-axis. I’m taking a value of $-10~text{Nm}$.
I thought to apply a simple passive coordinate transformation on the moment vector.

$$A = left[begin{array} & cos{theta} & sin{theta} -sin{theta} & cos{theta}end{array}right]$$
Choosing a $theta = 10^circ$ (rotating the axes counter-clockwise by $10^circ$, please correct me if I’m wrong), I get $M_z’$ as
$$M_z’ = A, M_z = left[begin{array} & cos{theta} & sin{theta} -sin{theta} & cos{theta}end{array}right]left[begin{array} & 0 -10end{array}right] = left[begin{array} & -1.736 -9.848end{array}right]$$
I’m not sure how to interpret this. I am probably missing something very basic, but is this the moment about the new z-axis? Shouldn’t it be a single number? Please advise.