There's a tag that relates to the Zhentarim:

<?xml version="1.0" encoding="UTF-8"?>
<save>
<version major="4" minor="0" revision="0" build="19"/>
<region id="Tags">
<node id="root">
<attribute id="Description" type="LSString" value="Player has been recruited by the Zhentarim."/>
<attribute id="DisplayDescription" type="TranslatedString" value="" handle="h204da519g01abg4ecbgbeafg603c52d65312"/>
<attribute id="DisplayName" type="TranslatedString" value="ZHENTARIM" handle="hb87dd233g344fg4a9cgaba5gd322aa79afc6"/>
<attribute id="Icon" type="FixedString" value=""/>
<attribute id="Name" type="FixedString" value="ZHENTRECRUIT"/>
<attribute id="UUID" type="guid" value="7ba800bc-5a08-428c-bb72-0fa2b61e2673"/>
<children>
<node id="Categories">
<children>
<node id="Category">
<attribute id="Name" type="LSString" value="Dialog"/>
</node>
<node id="Category">
<attribute id="Name" type="LSString" value="Story"/>
</node>
</children>
</node>
</children>
</node>
</region>
</save>

Could just mean you helped get the chest back and now they know you/like you.