How to deal with the resource identifier field that might need to be a dc doi?

[physikerwelt]

From http://schema.datacite.org/meta/kernel-4.4/metadata.xsd

<xs:element name="identifier">
<xs:annotation>
</xs:annotation>
<xs:complexType>
<xs:simpleContent>
<xs:extension base="nonemptycontentStringType">
<xs:attribute name="identifierType" use="required"/>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>

Our OAI-OMH identifiers currently have the following form.
oai:zbmath.org:7761743

While this is most likely valid to the xsd spec, it does not confirm with the description in the PDF which seems to expect something like <identifier identifierType="DOI">10.5072/example-full</identifier>