Complex sentence: The toxicity of carfentanil has been compared with nerve gas according to the Associated Press article, which quoted Andrew C. Weber, Assistant US Secretary of Defense for Nuclear, Chemical and Biological Defense Programs from 2009 to 2014 as saying It's a weapon.
Split into simpler sentences: The toxicity of carfentanil has been compared with nerve gas, according to the Associated Press article. The article quoted Andrew C. Weber, Assistant US Secretary of Defense for Nuclear, Chemical and Biological Defense Programs from 2009 to 2014 as saying It's a weapon.