How can I zoom in and out in Helix with SharpDX with C#

I try to zoom in and out in the code behind.

<hx:Viewport3DX
            Name="Viewport"
            BackgroundColor="Black"
            Camera="{Binding Camera}"
            EffectsManager="{Binding EffectsManager}"
            ShowViewCube="False">
</hx:Viewport3DX>


public OrthographicCamera Camera { get; }

public void ZoomIn()
{
  var newPosition = new Point3D(Camera.Position.X, Camera.Position.Y, Camera.Position.Z * 1.5);
  Camera.AnimateTo(newPosition, Camera.LookDirection, Camera.UpDirection, 500);
} 

but nothing changed.

The Camera.Position.Z was changed but not the view of hte application.

Any suggestions?

Greeting Michael