When doing a three-column div output like Zen Cart is out of the box you have to set the divs and the css to a particular sequence in order to have the columns show up in the browser as left, middle, and right. It's one of the reasons things can get so screwed up if someone tries to "delete" a column in a php file and why the geniuses at ZC have set up switches to turn columns on and off at will.

Now, all you need to do for the client is set up that particular sequence inside the original middle column without messing up any of the wonderfulness that is Zen Cart. But that's not all. You'll need to accurately tell Zen Cart exactly what goes in ALL the new columns.
For an extra degree of difficulty, let's make sure that the columns are even. Easy in Word, right? Not so easy in the sitemap when we are using a lot of code to pull data in.

Worst of all..... One bad bit of code and the confused SE is not going to bother with reading the sitemap.

I would advise the customer that putting lipstick on this pig would require the purchase of Revlon AND Maybelline. I would venture to say that most customers use search and seldom even glance at the sitemap.

If it's their way or the highway, Google three column div layout and take a look at some of the examples. One of the best is http://matthewjamestaylor.com/blog/perfect-3-column.htm.