MZEE is defined in lesser dictionaries as "older person, elder" ....but I am surprised to see it so defined in the OED!
In my experience in East Africa in the 1970s ....and I doubt things have changed... the word meant : Older MAN , Elder. It is a term of great respect, for example, Mzee Kenyatta. OLD, here, has only positive values, wise, experienced, successful, great, a survivor, etc. None of the somewhat common negative Western thoughts...senile, decrepit, lame, dependent, and so on. I have never heard Mzee used for a woman.
I wonder whether political correctness has crept in. Believe Mzee is a word of "black patriarchy" which is interesting in these times of blaming the other one for all our troubles.