There are 3 fonts defined for you in the standard zwgc. They are "courier", "helvetica", and "times". To use one of them, you can modify the print statements in your .zwgc.desc file. For example, changing the line
will cause the body of your messages to be printed in the Helvetica font.
You can also send someone a message in times by just putting the font command in the text of the message. For example, I could zwrite to you and put:
in the message, and the times font would be used for the second line. Anything that is not specified in a different font will use the default font (which is set to courier by default), but the default font can be changed, if you like. For more information on how to do this, please see "How do I change the default font for Zephyrgrams?".