[edulid]

You can see also in the following screenshot that the zoom-chart is not showing anything although there are two datapoints in the main chart:

[Isomorphic]

You're using autoDeriveSchema and the SQL schema uses a datetime type, so your field is of type "datetime". Add an explicit declaration that you want the field to be type "date" to correct the issue.

[edulid]

You are right, thanks.

The second issue with the empty zoom-graph, are you able to reproduce this ?

[Isomorphic]

There's no way to show a functioning zoom interface when there are two data points.

Let us know if you see a similar problem in a case where zooming actually makes sense.