Sorry, but it is for sure that Bonnier got one of the 6C3000 spiders to Sweden and used it for ice razing.
But if the Zagato is a re bodied coupe , I don't know. My impression was that he have had an accident and got the spider repaired by Zagato.
But it is interesting if the Zagato/Bonnier is build on a coupe chassis.
It has to be examined
http://www.gpracing.net192.com/drivers/careers/75.cfm
That year Bonnier also took part in the Swedish GP, a sportscar race with a Le Mans start. Bonnier's start was spectacular if not too successful: he got into reverse gear by mistake and crashed into the pits! Bonnier continued racing in rallies and ice races. As an Alfa distributor he was able to borrow one of the few Alfa Romeo "Disco Volante" 3.5-litre sportscars in existence. While not much of a sports car the Disco Volante proved to be the ideal ice racing car and after an unsuccesful debut at the Finnish GP Bonnier went on to score several Scandinavian successes.
http://8w.forix.com/bonnier.html