you call yourself an ecommerce website builder - but you do not support the native ecommerce tracking features of Google Analytics - certainly the most popular web analytics package available in 2013.
This is an open letter to Zeald to try to convince you to consider supporting this feature, by default, for no extra charge for your existing customers. If you did support it, the thanks page for a conversion mite include calls to _addTrans, _addItem and _trackTrans, and would allow your clients to see the last traffic source before a conversion - whether it be from any source, Bing, Facebook, Yellow etc, not just Google Adwords. Not only that, but they would be able to see a plethora of multi-dimensional reports that could show average order value, top products, and feed the conversion value easily back into Adwords to enable true ROI calculations to be made for all traffic sources.
Once you have got this working - I'll convert this blog post into a thank you message.
Yet I see no mention of support in your help files, only this one which is about a different tracking method that only works for Adwords:
Adwords Conversion Tracking != Google Analytics Ecommerce Tracking.
To help you get going, below is an example of what the tracking scripts look like: