The Zoomer was, indeed, an antenna float fixed top and bottom. Ivan invented it originally for fishing the Welland, which for much of its wide length runs South-East to North-West, and often used to have movement. The wide Welland extends for a comparatively short length from Peakirk to Spalding, (perhaps ten miles). Above this the narrow Welland (which used to run across the bottom of my garden in Market Deeping) is flowing most of the time, except in a hot summer, and that runs into the wide Welland at Peakirk, giving it some movement a lot of the time.
Match fishing always took place on the Western bank, which gave anglers an upstream wind in the prevailing West/North-Westerlies. The Zoomer was weighted mainly under the float - enough weight to allow a long cast (up to 40 yards) to pick up the flow, which tended to be on the far side, as that was the easiest side for dredgers to work when they deepened the river. The rod was held high, and the rig fished like a stick float, with the wind holding the line upstream. This picked up any movement in the deep channel.
The cast had to be careful - a high looping cast to avoid tangles, and to allow the rig to land close to the far bank rather than the quick lash which you would normally give a bottom-only waggler float, but which would result in the bait flying ahead of the float.
Conditions had to be near-perfect for the Zoomer to work, of course.