Haven't really looked much into it, but in the XML files, at the top, you have to name the related schema file, which has to be in the same folder (this whole schema thing only applies for modular loading).
And e.g. in your EquestrianMissionary_CIV4UnitInfos.xml you have:
but the schema file in the folder is named Elements_of_Harmony_CIV4UnitSchema.xml.
And e.g. in your EquestrianMissionary_CIV4UnitInfos.xml you have:
PHP:
<Civ4UnitInfos xmlns="x-schema:AltReligions_CIV4UnitSchema.xml">
but the schema file in the folder is named Elements_of_Harmony_CIV4UnitSchema.xml.