How can I prevent iTween from scaling my object to 0 when using ScaleTo method?

I am trying to scale my object to a vector of 8, 8, 8 and then back down to a vector of 1, 1, 1. For some reason, as soon as the script runs the object scales itself down to 0, 0, 0, and it doesn't change its scale at all after that. Here is the code that I am using. Thanks!

 void Update()
     {
     if (lefthand.transform.rotation.z >= 140 && lefthand.transform.rotation.z <= 200)
         {
         iTween.ScaleTo(movement, menu2, 2);
         }
     else if (lefthand.transform.rotation.z < 140 || lefthand.transform.rotation.z > 200)
         {
         iTween.ScaleTo(movement, menu1, 2);
         }
     }