You can import an old offline file. But be careful, the other direction is not possible.
There is no longer a simplified ZHprivateTax-light online version. The ZHprivateTax online has all the forms, but looks different than the offline version. In the last three years there was the light and full online version.
The most important part of the data import is the Wertschriftenverzeichnis and the possibility to compare the entered values with one from the previous years.
This isn't quite correct. You fill out and submit everything on line, but you still have to send some documentation (i.e. salary certificates etc...) via post.