请教大全88里面的两句话的语法结构,请NN帮忙

1. Shaw, whose essential modesty is as disarming as his pose of vanity is disconcerting,assigns to himself the role, not of the master, but of the pioneer, the role of
a Marlowe rather than of a Shakespeare.

2. No one, says Shaw, will ever write a better tragedy than Lear or a better opera than Don Giovanni or a better music drama than Der Ring des Nibelungen;  but just as essential to a play as this aesthetic merit is moral relevance which, if we take a naturalistic and historical view of morals, it loses, or partly loses, in time.
 

这两句的红色部分语法结构是什么呢？如何翻译？还没搞懂，请NN帮忙

ding

多谢回答，which和if应该是修饰moral，但it lose是个完整得句子，which引导的句子是哪个呢？