A Zeon spacecraft was a type of pre-warp spacecraft utilized by the Zeon of planet Zeon.
Spock stated of Zeon ships, that the Zeons had "a crude interplanetary capability", and took no note of peculiarities in their known technology and the reaction powered Ekosian missile encountered by the USS Enterprise in 2268.
During the Enterprise's orbital approach on neighboring Ekos, the Ekosians launched a thermonuclear missile at the incoming vessel, later stating that they repulsed "an attack by Zeon spacecraft," and that their "missiles utterly destroyed the enemy," much to the contrary.
Later, it was revealed that Melakon launched a space fleet sent to invade Zeon, using Zeon's own technology against them. The fleet of Ekosian ships carried with it "thousands of Ekosian spacemen." While Daras begged Captain James T. Kirk to have the Enterprise destroy the fleet, Kirk opted to revive John Gill and have him persuade the Ekosians to do it themselves. (TOS: "Patterns of Force")
These spacecraft were only mentioned in dialogue.