// Variant A (Working for Start > End and Start < End)
protected virtual void LerpTransformLinear(Vector2 startpos, Vector2 endpos,
                                           float startzoom, float endzoom, float ammount)
{
   // set private Position field to lerp between the Start Position and the End Position of the given Ammount.
   m_position = Vector2.Lerp(startpos, endpos, ammount);
   // set private Zoom field to lerp between the Start Zoom and the End Zoom of the given Ammount.
   m_zoom = MathHelper.Lerp(startzoom, endzoom, ammount);

   // Set private Matrix field to a new Matrix of the private Position, the private Zoom and the private Viewport size.
   m_transform = CreateTransform(m_position, m_zoom, new Vector2(Viewport.Width, Viewport.Height));
}

// Variant B (Working for Start > End, but not Start < End)
public static void LerpTransformLinear(out Matrix matrix, Vector2 viewsize,
                                       Vector2 startpos, Vector2 endpos,
                                       float startzoom, float endzoom, float ammount)
{
   // Create Position from a lerp between the Start Position and the End Position of the given Ammount.
   Vector2 position = Vector2.Lerp(startpos, endpos, ammount);
   // Create Zoom from a lerp between the Start Zoom and the End Zoom of the given Ammount.
   float zoom = MathHelper.Lerp(startzoom, endzoom, ammount);

   // Set given Matrix to a new Matrix of the created Position, the created Zoom and the given Viewport size.
   matrix = CreateTransform(position, zoom, viewsize);
}

public static Matrix CreateTransform(Vector2 position, float zoom, Vector2 size)
{
   // return a new Matrix of the given Position, Zoom, and Viewport Size.
   return Matrix.CreateTranslation(new Vector3(-position.X, -position.Y, 0f)) *
                  Matrix.CreateScale(new Vector3(zoom, zoom, 1f)) *
                  Matrix.CreateTranslation(new Vector3(size.X / 2f, size.Y / 2f, 0));
}