Looks good, Black. I like the ZOC part of the Zulu UA. The Sumerian UA and UB might be a little bit too powerful given the start bias. Maybe the Ziggurat shouldn't provide culture, particularly as the rivers are going to provide enormous amounts of culture.
Edit: Perhaps the Sumerians could have the onager as a UU (chariot replacement): no horses required, able to melee attack as well as ranged, and no penalty for attacking across rivers.
Edit: Perhaps the Sumerians could have the onager as a UU (chariot replacement): no horses required, able to melee attack as well as ranged, and no penalty for attacking across rivers.