When creating multiple connections between the same nodes in Zest the connections will not be distinguishable, but will display "on top of" each other. This is in contrast to what you typically get with dot.
For illustration, I have here rendered the following dot file:
...using Zest/Dot in Zest 2 and the built-in Zest Graph looks like this:
...and when rendered with dot I get this:
The second image is typically what I want in regards to the edges (for a multitude of reasons I would like to use Zest, however). Notice also that the self-connection is much more visible here.
Unfortunately, this is currently only supported in GraphViewers (see [1] for a sample), but not for plain Graphs (which are created by the DOT support). Contributions are very welcome - see [2] for details on what we have so far.