{
    "header": headerDoc,
    "footer": footerDoc
}

const headerDoc = new Docxtemplater().loadZip(new JSZip(headerZip))
const footerDoc = new Docxtemplater().loadZip(new JSZip(footerZip))

const doc = new Docxtemplater();
const inputZip = new JSZip(docX);
doc.loadZip(inputZip)
	.setData({
		header: headerDoc,
		footer: footerDoc,
	});
const subtemplateModule = new SubtemplateModule();
doc.attachModule(subtemplateModule);
const output = doc.render().getZip();