Think of it in terms of venn-grams; "field of endeavor" is a much broader descriptive of human activity, but it is one which includes "inquiry". For instance, one can "endeavor" to excel through one's "inquiry" into the more esoteric scientific disciplines. One can "endeavor" to cure cancer, as well, which would of course include several "fields of inquiry" -- medicine, biochemistry, etc.
Basically, "field of endeavor" describes a person's general psychological and spiritual comportment towards a range of activity, while "field of inquiry" describes a more particular range of activity ("inquiry"); or, in other words, "endeavor" describes why, or how one does something, while "inquiry" describes what.
Since "inquiry" can be an object of endeavor, it's clear the two can overlap.