TNG "Peak Performance"
In preparation for the first Starfleet combat exercise in living memory, the USS Enterprise receives a Zakdorn advisor/observer named Kolrami, who will report on the crew's performance. Kolrami is present because of the Zakdorn reputation for having the greatest innately strategic minds in the galaxy. Kolrami establishes his credentials by easily defeating both Commander Riker and Data in a game called Strategema.
Later, when the combat exercise becomes a genuine crisis due to the unforeseen arrival of a Ferengi pirate ship, Kolrami proves to be quite useless. Closing out the show, Data forces Kolrami to concede a Strategema rematch by switching his tactics from trying to achieve victory conditions to maintaining a stalemate, taking advantage of his android endurance to outlast the Zakdorn, who is unable to adapt to Data's change of strategy.
A Federation surplus depot is managed by a Zakdorn named Dokachin. In the episode, his planet of origin is irrelevant to the story.
The Zakdorn reputation for strategic brilliance appears to be entirely undeserved. As Worf pointed out in "Peak Performance", their reputation means nothing, since no one has tested it in millenia. The fact that Kolrami is a master of Strategema says little about his effectiveness in a real war or battle, and his only suggestion when faced with a genuine threat was to retreat. Furthermore, the Federation has been involved in hostilities to varying degrees with the Klingons, Romulans, Cardassians, Talarians, and Dominion in recent memory, but the Zakdorns have never been seen contributing to Federation strategy in these conflicts.