I take it you're fairly new to Zen Cart? If so, there is a lot of info in the Tutorials/FAQ linked above.

Look for switches in admin/Configuration. If you take your time and wade through it, you'll find a lot of things you can turn off.

Besides the things you can adjust under Configuration, make sure to check out admin/Tools/Layout Boxes Controller, where you can hide a lot of things you won't need.

You may also want to consider using EZ pages rather than the stock cart pages. Read about them in the FAQs above.

Look here in the forum for threads that address the possibility of a single page/single product setup. Once you've got that, then work hard at the stylesheet to arrange and style things to your liking.

Also have a look at the various mods (Free Software Add Ons, link above left) especially under checkout.

That ought to get you started.

Rob