I got it to work using Document.Text. Here's the code, in case someone else is looking to do the same:
WebBrowser1.DocumentText = _
"<!doctype html><html lang='en'><head>" & _
"<meta charset='utf-8'><meta http-equiv='X-UA-Compatible' content='IE=edge'>" & _
"<body>" & _
"<script src='" & _
IO.Path.GetFullPath(".\zoomcharts\lib\zoomcharts.js") & _
"'></script>" & _
"<div id=""demo""></div>" & _
"<script>" & _
"var t = new TimeChart({" & _
"container: document.getElementById(""demo"")," & _
"area: { height: 350 }," & _
"data: {" & _
"preloaded: {" & _
"values: [" & _
"[0, 100]," & _
"[1000, 200]," & _
"[2000, 300]," & _
"[3000, 400]," & _
"[4000, 500]" & _
"]," & _
"unit: 's'" & _
"}," & _
"timestampInSeconds: true" & _
"}" & _
"});" & _
"</script>" & _
"</body>" & _
"</html>"
Just starting into it, it seems DocumentText is the more direct way of creating the chart. I'd have to look into using window.external and eval() - maybe that's a cleaner approach. If someone wants to show a sample of how it could be used specifically with these charts I'd be interested in seeing it.