ZET has a Swiss Ephemeris module licensed from Astrodienst.
The main Swiss Ephemeris files, distributed in the ZET Lite download, are the following:
You can find a comlete description of the Swiss Ephemeris at www.astro.com.
Here is a brief extract about the ephemeris and its component files, by its authors:
The core part of Swiss Ephemeris is a compression of the JPL-Ephemeris DE406. Using a sophisticated mechanism, we succeeded in reducing JPL's 200 MB storage to only 18 MB. The agreement with DE406 is within 1 milli-arcsecond (0.001). Since the inherent uncertainty of the JPL ephemeris for most of its time range is much greater, Swiss Ephemeris should be completely satisfying even for computations demanding very high accuracy.
The time range of the JPL ephemeris is 3000 BC to 3000 AD or 6000 years. We have extended this time range to 10'800 years, from 2 Jan 5401 BC to 31 Dec 5399. The details of this extension are described below in section 2.1.5.
Each Swiss Ephemeris file covers a period of 600 years; there are 18 planetary files, 18 Moon files and 18 main-asteroid files for the whole time range of 10'800 years.
The file names are as follows:
You can obtain these files from ftp://ftp.astro.ch/pub/swisseph/ephe/.
To download and install additional asteroids files, see Catalog of Asteroids.
If you already have astrology software which installed Swiss Ephemeris files, you do not need to retain ZET's copy of them. They can be accessed by ZET if you specify a path to them (see General Settings).