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:
Unfortunately, this is currently only supported in GraphViewers (see  for a sample), but not for plain Graphs (which are created by the DOT support). Contributions are very welcome - see  for details on what we have so far.