That is an out of memory error. If you have a computer with lots of RAM
and a 64bit version of windows, install the 64 bit version of calibre,
that may let you convert this document. Otherwise you are out of luck.
12GB of RAM on an i7 running Windows 10 x64 with Calibre x64 installed.
The 67.8mb mobi just sits at 1%, a smaller mobi from them (The Oxford Dictionary of Idioms) 1mb takes a while but gets converted.
That is an out of memory error. If you have a computer with lots of RAM
and a 64bit version of windows, install the 64 bit version of calibre,
that may let you convert this document. Otherwise you are out of luck.
status wontfix