Fermat's Last Theorem for even indices

Question

My question is related to Fermat’s Last Theorem for even indices. Searching through the internet I came across a book – 13 Lectures on Fermat’s Last Theorem written by Canadian Professor of Mathematics and Statistics , Paulo Ribenboim. Therein he shows that the first case of FLT has been proven for even indices where

1. first case of FLT means $x^n+y^n=z^n$ where $n∤xyz$ and
2. the second case of FLT is where $x^n+y^n=z^n$ and $n|xyz$ and $gcd⁡(x,y,z)=1$

In the book it is mentioned that G. Terjanian had proved the first case of FLT.

My question : Prior to Andrew Wiles monumental work did any mathematician prove the second case of FLT for even indices ? Any reference to such work would be appreciated