localEulerAngle.z to a float Y axis

Hello everyone, i have a simple math question, i have a obj and i have the local Z angle of this obj, i need convert this Z angle to Y axis, but remaining LOCAL not global.

I have a WRONG example but i almost came close to what I want with it:

 var obj1: GameObject;
 var zAxis: float;
 var axisAngle: Vector3;
 
 function FixedUpdate(){
 obj1.transform.localRotation.ToAngleAxis(obj1.transform.localRotation.z, axisAngle);
 
 zAxis = axisAngle.z;
 }
 

It converts to axis (min = -1, max = 1) BUT it is not as "local" when obj1 changes its rotation X, this float value changes, and I do not want that to happen.

I am creating an object that "balances" the Z axis, and this axis when it rotates, the other object rotates on the Y axis