I guess that you mean a comparison of the near to mid term mortality risk associated with
MUAC < 125 mm & WHZ > -2 (MAM MUAC-only)
and:
MUAC < 115 mm & WHZ > -3 (SAM WHZ only)
I alos assume tha you want mortality in untreated cases found in the community.
Looking at the literature you will probably find results for
all MUAC < 125 mm
and:
all WHZ < -3
which will not answer your (very specific) question. Looking at the literature that reports results from community-based cohort studies we find that all WHZ did not work well at predicting near to mid term mortality in all cohorts. You can see this in this review:
Pelletier, D. L. (1994). The relationship between child anthropometry and mortality in developing countries: implications for policy, programs and future research. The Journal of Nutrition, 124(10 Suppl), 2047S–2081S.
I have put this review here.
I have some data here from 11 countries collected in cohort studies running between between 1977 and 1997 and could run a bespoke analysis to answer your specific question. I would need to seek permission form the data owners to do this.
Sorry not to be of more help.