I think it is because this Is the Zodiac version of the Zephyr, according to Wikipedia.
https://en.wikipedia.org/wiki/Ford_Zephyr
Zephyr Zodiac (or Zodiac Mark I)
Overview
Production
1954–1956
Body style
4-door saloon
5-door estate (conversion)
Powertrain
Engine
2,262 cc (140 cu in) straight-6
Dimensions
Curb weight
2,680 lb (1,215 kg)
Model number EOTTA
The Zephyr Zodiac (or Zodiac Mark I) was an upmarket version of the Zephyr launched at the London Motor Show in autumn 1953. It had two-tone paintwork, leather trim, a heater, windscreen washers, whitewall tyres, and spot lights. The engine had a higher compression ratio – 7.5:1 instead of 6.8:1 – increasing the maximum power to 71 bhp (53 kW).[6]
A car tested by The Motor magazine in 1955 had a top speed of 80 mph (130 km/h) and could accelerate from 0-60 mph (97 km/h) in 20.2 seconds. A fuel consumption of 22.2 miles per imperial gallon (12.7 L/100 km; 18.5 mpg-US) was recorded. The test car cost £851 including taxes.[6]
There are no official records of Zephyr Zodiac convertibles being produced, but there were a few estate cars.