Complex sentence: Allison Schroeder wrote the script, which was developed by Gigliotti through Levantine Films, and which also would produce the film along with Peter Chernin's Chernin Entertainment.
Split into simpler sentences: Allison Schroeder wrote the script, which was developed by Gigliotti through Levantine Films. That firm produced the film along with Peter Chernin's Chernin Entertainment.