If you just want to use ZFE programatically in your web page without showing it, add headless: true to your ZFE constructor options.
<script src="http://zfe.company.com:7070/zfe/connector/zfe-embed-sdk.js"></script>
<script>
var zfe = new ZFE.ZFE({
url: 'http://zfe.company.com:7070/zfe/',
headless: true
});
zfe.connect().then(function () {
zfe.getSessionManager().getDescriptors();
});
</script>