Complex sentence: Late 2014 saw the return of Marta with new material, on September 23,2014, "La Que Nunca Se Rinde" was released on iTunes and a new album with unedited material was announced been in the works.
Split into simpler sentences: Late 2014 saw the return of Marta with new material. On 23 September 2014, "La Que Nunca Se Rinde" was released on iTunes and a new album with unedited material was announced been in the works.