同意English expert的解答。其实，这等同于not so much...as句式。

1.not so much A as B = not so much A, but B = less A than B = more B than A = B rather than A。如：

Experience shows that success is not so much due to ability as to zeal. 经验表明，成功与其说是由于能力，毋宁说是由于热忱。

= Experience shows that success is not so much due to ability, but to zeal. (but前常有逗号)

= Experience shows that success is less due to ability than to zeal.

= Experience shows that success is more due to zeal than to ability.

= Experience shows that success is due to zeal rather than to ability. 

2. 如果so much...as句型中的so much与not分离而去和as连用（即构成not A so much as B），意义完全一样。如：

It is not so much advice as approval that he seeks. 他所追求的不是忠告，而是赞赏。

= It is not advice so much as approval that he seeks. 

▲not so much as...“连……也不”，意义同not even。如：

I have not so much as heard his name. 我连他的名字也不曾听说过。

He had not so much as his fare home. 他甚至连回家的路费都没有。