On the Zippy website, there is a guide to understand the strip. Supposedly, you can get the gist in 6 easy lessons. But, as the site points out in a Mark Twain quote, "Analyzing humor is like dissecting a frog---the procedure kills both."
Also, on the website, you can take a roadside tour to places Zippy has visited. Since I am living in Illinois, I checked that out and only found three strips.
1. The giant 62 foot Abraham Lincoln by Charleston, made by the same folks who brought you Fairchild the Gopher who graces the Minnesota State Fair.
2. Superman in Metropolis.
3. An elephant sipping a dry martini wearing dark glasses, but didn't say where it was.
Love That Zippy. --RoadDog
William Whistler-- Part 1: Over 60 Years in U.S. Army
34 minutes ago