Much harder,of course, is changing a system that let companies take the risks that led to the current financial crisis.

当然，更难的是改变一个让企业承担导致当前金融危机的风险的体系。

以上为表语提前句首倒装结构

改为陈述语序为下面句子

Of course, changing a system that let companies take the risks that led to the current financial crisis（主语）//（系动词） is//（表语） much harder 

重点短语和结构解析如下

(1)changing a system that let companies take the risks that led to the current financial crisis为动名词短语作句子主语

(2)a system为动名词changing的宾语成分

(2)that let companies take the risks that led to the current financial crisis为定语从句修饰动名词changing后面的的宾语“a system”

(3) that led to the current financial crisis为定语从句修饰定语从句的中的名词“the risks”

(4)let sb/sth do sth 让..做某事

(5)lead to 导致，引起