Yus - the traditional cake in Latin America and the Balkans is a descendant of things like trifle or bread pudding usually called tres leches or trileçe ("three milk") and uses condensed milk, evaporated milk, and whole milk. I think seis leches is a joking extension of that.
Sí
So like cow milk, goat milk, what are the other four?
I can barely afford 1 :’-(