This is from a developer's perspective. I believe that Zoho should try to correct it as early as possible because it is setting a bad example for other developers.
The HTML image width and height would only do harm to the image and I believe from the code level the image has to be changed before rendering preserving the aspect ratio. I would like to share an article in .NET http://www.dotnetspider.com/resources/3020-Quick-Effective-Tips-Image-API-Input-Validat.aspx which can help this. I think since Zoho is a Java suite you may need to adopt a similar trick to address this issue.