I am guessing that the Zoombox is that projector with a built in DVD player built in, right? (I saw a commercial for it once, seemed pretty interesting)
Anyway, since the Zoombox does not have a tuner, you will need some sort of tuner
You can use a tuner found in VCRs or standalone DVD-RWs (like a VCR, but instead of recording to VCR tapes, it recordes to DVD-R and DVD-RW discs, or DVD+R and DVD+RW discs, it has a tuner like the ones found in VCRs), you plug your cable into the VCR or DVD burner, then take the composite out (yellow/red/white) and connect that to the zoombox, then use the VCR or DVD burner to change channels
You can also now get a digital tuner, this will allow you to watch some digital stations that your cable company may be putting out, look for a digital tuner that had analog pass-thru (this will allow you to watch new digital channels, but also allow you to watch your normal cable), just connect the cable to the digital tuner, then take the composite out (yellow/red/white) to the Zoombox, then change channels through the digital tuner, and have fun finding new channels