Hi,
VML is strange – it looks like XML, but it is not.
There is, I recall, a way to ‘hack’ the VML so that it can be read by an XML parser, but I don’t recall the details.
Right now, I am fully engaged in completing a module that enables comparing two DOCX files and producing another file that contains tracked revisions, and contractually need to finish this ASAP, so can’t spend any time researching this. However, I do recall doing this at one point.
Question – why are you using a presentation that contains VML? It is deprecated. If you load the presentation in PowerPoint, and then specify the right option, then I believe that you can save the presentation in such a way that it replaces VML with DrawingML.
-Eric