How can I listen to saved messages from history files?

Yes, you can do this by using the history export command line utility for Windows. 

The tool will parse Zello history files and export messages (one message per file) and the plain text index of messages in a file called history.txt. Audio messages are exported without transcoding, so use Speex codec with OGG container or AMR codec.

You can listen to the messages in these formats using VLC player http://www.videolan.org/ or transcode them to mp3 / wav using ffmpeg http://www.ffmpeg.org/.

One way to use the utility is to create a scheduled job for daily export of history from certain PCs and upload to any location they want. The utility allows exporting messages within specified time interval, which can be used to avoid duplicates.

Download from http://zello.com/data/mesh/hex.exe. Use --help command line to see a short help.

 

For a step by step guide on how to use the history tool refer to History Tool Guide.