Complex sentence: The Chism's were not filmed during the Zapruder film because they were hidden by the "Stemmons Freeway" sign, but, they are clearly visible in many other films, photos, and slide-photos captured before, during, and after the assassination.
Split into simpler sentences: The Chism's were not filmed during the Zapruder film because they were hidden by the "Stemmons Freeway" sign. They are all clearly visible in many other films, photos, and slide-photos captured before, during, and after the assassination.