3rd party apps importing/linking to Zoho docs

3rd party apps importing/linking to Zoho docs

I'm a big fan of the notion of CREATING (not just storing) documents online. For purposes of this question I'll refer to Zoho Writer. However, it seems the productivity advantages of working online using Zoho Writer are lost when you want to share created document with another 3rd party app you are using - let's say a group collaboration site such as Central Desktop.

I've yet to find an example where you can directly import/link to your document created in Zoho. The typical method requires you to i) first download Zoho Writer doc to desktop, and then ii) upload to Central Desktop.

Is this lack of "cloud-to-cloud" importing a technological feat that hasn't been overcome OR is it more influenced by privacy/legal/business reasons (i.e. identity validation between the two app providers)?

Thanks,
Andy