How to convert ecore (EMF) to xsd

What is the best way to convert .ecore-files into .xsd-files?

You need to have the feature XSD Ecore Converter installed (it's part of the EMF project).

Then you can open the context menu on your ecore's generator model (extension .genmodel) and select Export Model. It should offer you now to export the ecore to XML schema.

In Eclipse, when only EMF SDK is installed, you may not be able to see the model exporter for "XML Schema". (On my side, only "UML model" is visible).

Use an update site with EMF repository. Install the XSD features then the exporter would appear.