Complex sentence: Between 1991 and 1994, Amenábar made four short films which in a very significant way influence his first full-length films, La Cabeza (short), Himenóptero (short) and Luna (short).
Split into simpler sentences: Between 1991 and 1994 he made four short films that in a very significant way influence his first long/full length films. La cabeza (short) Himenóptero (short) and Luna (short).