His page for the first zonal, Caracas 1951 (C02), includes the following explanation (translated from the original Spanish by Google):-
Since 1950 Venezuela joined the FIDE Zone no.6, which covered the region of Central America and the Caribbean. In 1951 the Venezuelan doctor Manuel Acosta Silva was appointed Vice President of FIDE for the Central American and Caribbean Zone, in office continuously until 1966, when it was replaced by the Cuban A.I. José Luis Barreras.
Later the zone was officially numbered '7', then '8', then '2.3', which it remains today. Thanks, Rafael, for clarifying the early record of an entire zone.