He could not answer (neither of )(either of ) the quations I

是这样的 这里应该是选择either of,因为这句话想构成的是一个否定句,而且前面已经给出了否定此not.
如果是同样的意思的一句话,用neither of 来回答,那就是He could answer neither of the questions i asked. 但前提条件是question只有两个,更多就是none of.
Is that clear?