You will get channels that are analog, 02-126 (not always do cable networks use analog through 126)
You will get the local broadcast channels as QAM. Maybe a few more.
If you use the cable box and the ZephIR, you'll get all the channels as analog, but you'll get them all.
If you use the cable box to the composite inputs (the cable dongle to the side of the EyeTV hardware) and the coax to a splitter right before the cable box, so that they both get the signal directly, then you'll be able to potentially get the best of both worlds, but you'll have to set it up twice - once to autotune with the ZephIR, and once to autotune with the coax for QAM.