这里than后面为何用directing呢

It could let foreigners settle cross-border transactions directly in central-bank money, which would be faster, cheaper and safer than directing them through a web of “correspondent” banks. 

请问老师这里的than后面用directing，是than做介词的使用方法吗，那这里能不能用than directs them through...

譬如这句，The question is more complicated than appears on the surface.

which指代的是let foreigners settle cross-bordertransactions directly in central-bank money，which定语从句等于：

Lettingforeigners settle cross-border transactions directly in central-bank moneywould be faster, cheaper and safer than directing them through a web of “correspondent” banks 如此你就能看出directing动名词短语为比较分句的主语，省略了系词be。表语为比较对应项，需要省略。