Lord Lakely
Idea Fountain
Emperor is perfectly winnable, but Zulu is not the easiest Civ to learn the game with if you're going to play passively. Try a civ with an easier learning curve, such as Arabia and Korea and keep on practicing. I won my first emperor gave as Australia and recently have won games as Sumeria and Georgia. It takes time to adjust to and personally, I prefer playing on King, so there's no shame in failing on Emperor. The game is supposed to be fun 
Anyway,
The only differences are that the AI gets compared to King is a +20% prod bonus (meaning: earlier districts and more wonders) and an extra settler (and a lot of extra units but that's less of a problem.)
So, to catch up, you need to gain cities, either through ancient era conquest (if Sumeria, Nubia, America, Sparta, or Aztecs) or through settling them (anyone else). Conquest is great if you can get an early Campus or Holy Site out of it (which you normally can). Consider taking a city state if you start as the Ottomans for easy Jannisary recruitment later. If you decide to REX instead, get the Gov Plaza + Ancestral Hall and Magnus with Provision asap, assign the Colonization card to your goverment. Then, spam settlers everywhere and settle every location that loyalty pressure allows. The extra pop will generate enough science to allow you to catch up to and remain on par with the AI.
Always check the AI's military, culture and science numbers, especially on Civs with no bonuses to towards Science or Culture (Rome/Greece will always be ahead in culture and Korea/Sumeria will always be ahead in science.) You cannot fall too far behind. Build Campuses and Theatre Squares when behind, or units if you have an unfriendly but stronger neighbour. I also build a CommHub or Harbour in every city to ensure I get the extra trade route. Internal trade + Magnus + Early Gov Plaza gives you a reliable prod and food yield for your new cities. This is especially good if you're Persia, Cree or Inca because of their buffed internal routes.
Espionage is important to prevent the AI from winning culture or science victory. Sabotage spaceports and steal works, level your spies up by syphoning funds.
IF you're hopelessly behind, aim for diplomatic or religious victory (if Russia, Japan or Arabia). Those are still feasable, regardless of how crap your army, science or culture gets.

Anyway,
The only differences are that the AI gets compared to King is a +20% prod bonus (meaning: earlier districts and more wonders) and an extra settler (and a lot of extra units but that's less of a problem.)
So, to catch up, you need to gain cities, either through ancient era conquest (if Sumeria, Nubia, America, Sparta, or Aztecs) or through settling them (anyone else). Conquest is great if you can get an early Campus or Holy Site out of it (which you normally can). Consider taking a city state if you start as the Ottomans for easy Jannisary recruitment later. If you decide to REX instead, get the Gov Plaza + Ancestral Hall and Magnus with Provision asap, assign the Colonization card to your goverment. Then, spam settlers everywhere and settle every location that loyalty pressure allows. The extra pop will generate enough science to allow you to catch up to and remain on par with the AI.
Always check the AI's military, culture and science numbers, especially on Civs with no bonuses to towards Science or Culture (Rome/Greece will always be ahead in culture and Korea/Sumeria will always be ahead in science.) You cannot fall too far behind. Build Campuses and Theatre Squares when behind, or units if you have an unfriendly but stronger neighbour. I also build a CommHub or Harbour in every city to ensure I get the extra trade route. Internal trade + Magnus + Early Gov Plaza gives you a reliable prod and food yield for your new cities. This is especially good if you're Persia, Cree or Inca because of their buffed internal routes.
Espionage is important to prevent the AI from winning culture or science victory. Sabotage spaceports and steal works, level your spies up by syphoning funds.
IF you're hopelessly behind, aim for diplomatic or religious victory (if Russia, Japan or Arabia). Those are still feasable, regardless of how crap your army, science or culture gets.