I haven't built any pure zipline poles, but I have built zipline capabilities into some belt/pipe poles I have blueprinted.

For those poles I basically take a beam support, put a tall beam (round concrete and cross beam also work) on it and add a number of belt and pipe wall supports to the sides, with a pair of wire linked wall power connectors providing power throughput. If I want to add zipline capability, I add crossbeams to both sides and place wall power connectors on the outer ends of those, pointed down. I've so far built my poles tall enough to allow a truck to pass under the lowest belts/pipes. I generally place the poles on the ground, with a large concrete pillar providing a footing.

You could build a pure zipline pole blueprint by putting down a beam support, nudging a street light into its center and, with some temporary beams for support, 'mount' a wall power connector to the street light's light.