if (Position != position || Scale != scale || Origin != origin || Rotation != rotation)
{
scale = Scale;
origin = Origin;
rotation = Rotation;
position = Position;
transform = Matrix.CreateTranslation(new Vector3(-Position.X, -Position.Y, 0)) *
Matrix.CreateRotationZ(Rotation) *
Matrix.CreateScale(new Vector3(Scale, 1)) *
Matrix.CreateTranslation(new Vector3(-Origin, 0));
}

This is exactly what I use, it works fine. Rotates around the center, zooms, translates, everything you wish for

EDIT: Origin is just your screen center. so in a 800 * 600 window, it is 400,300 vector.

This is exactly what I use, it works fine. Rotates around the center, zooms, translates, everything you wish for

EDIT: Origin is just your screen center. so in a 800 * 600 window, it is 400,300 vector.

if (Position != position || Scale != scale || Origin != origin || Rotation != rotation)                {                    scale = Scale;                    origin = Origin;                    rotation = Rotation;                    position = Position;                    transform = Matrix.CreateTranslation(new Vector3(-Position.X, -Position.Y, 0)) *                                         Matrix.CreateRotationZ(Rotation) *                                         Matrix.CreateScale(new Vector3(Scale, 1)) *                                         Matrix.CreateTranslation(new Vector3(-Origin, 0));                }

This is exactly what I use, it works fine. Rotates around the center, zooms, translates, everything you wish for

EDIT: Origin is just your screen center. so in a 800 * 600 window, it is 400,300 vector.

  if (Position != position || Scale != scale || Origin != origin || Rotation != rotation)
                {
                    scale = Scale;
                    origin = Origin;
                    rotation = Rotation;
                    position = Position;
                    transform = Matrix.CreateTranslation(new Vector3(-Position.X, -Position.Y, 0)) *
                                         Matrix.CreateRotationZ(Rotation) *
                                         Matrix.CreateScale(new Vector3(Scale, 1)) *
                                         Matrix.CreateTranslation(new Vector3(-Origin, 0));
                }

This is exactly what I use, it works fine. Rotates around the center, zooms, translates, everything you wish for