[Nickipedia]

From what I remember for older remotes without a back button, the zoom button actually sends different codes, than the zoom button on remotes with a back button sends. Someone with a first gen slide remote (no back button) should try and post how/if it works.

It must depend on what software is on the remote. The Zoom button on my Gen1 Mini IR remote doesn't work as a Back button. It simply gives the "bang" sound and doesn't do anything. The workaround is to hit TiVo and start over. Luck of the draw...