I think I've read ZatAoMM 3 times, admittedly the last time was >8 years ago. I didn't even remember "Gumption", it certainly did not seem to be a major theme of the book. It is very interesting to see other people's insights into a book especially when they're so divergent from your own. I guess I should read ZatAoMM and Lila again. :)
Gumption is what I remember the most about ZMM. The way I read it, the concept of Gumption felt like the backbone on which the rest of the book is built.
That and "Kulturbearer". :-)