Just recently started climbing the difficulties in this game, from Prince, then King, went to Emperor and won my first two out of three games, this is my fourth one and its looking to me like its too late to win. I play on Epic speed and random map.
What happened here is, the map was split into two continents and Shaka was on the second one. I was too focused on my own continent and fighting wars with several civs there but mainly focusing on science.
70-80 turns before the screenshot he just started snowballing the entire continent (now owning around 20+ world wonders, as for me around 15) and now came to conquer mine as well, attacking Korea and destroying them, so ofc I'm next.
Both me and Shaka finished Manhattan Project roughly at the same time but i still have 15 turns of research for Nuke, as I see that as my only strategy here.
As shown in the screenshot, his army is massive, 10x size of mine sooooooooo, am i too late?
EDIT: Some of you have asked for my social policies: https://imgur.com/a/lMXkbv0
EDIT: Demographics tab: https://imgur.com/a/demographics-0RMMqYq
FINAL EDIT: I tried the war and its just the war of attrition while he is progressing through science victory and me building nukes everywhere - overall maybe i could win at the end but it just became too boring managing world war so i let it go.