There's a few worlds/species whose affiliation with the Federation is unclear. Without citing any non-canon materiel (I'm looking at you, relaunch novels),
I don't see why you should ignore the novels.
But I'd say that the preponderance of canonical evidence re: Trill implies Federation Membership. Trill is a Member in the novels (Mission: Gamma
, Trill: Unjoined
This one's a bit trickier. The whole storyline of "Let He Who is Without Sin..." seems to put Risa as a member, but it's hard to reconcile that with Picard seemingly being unfamiliar with the planet and Riker explaining it to him in "Captain's Holiday".
"Without Sin" made it pretty explicit that Risa is a Member. That doesn't contradict "Captain's Holiday" -- in a Federation of over 150 worlds, is it really unreasonable to assume that not every Member's cultural practices are uniformly well-known throughout the rest of the UFP?
The novels also make Risa's Membership clear (TNG: Losing the Peace
Mordock was the first Benzite in Starfleet in "Coming of Age", but that doesn't necessarily mean anything. They could be a relatively new member or one whose members are typically interested in Starfleet. "A Matter of Honor" seems to indicate them not being members, based on Mendon serving as part of an exchange program and the Benzites said to be having their own ships (as opposed being "absorbed into Starfleet" like the Bajoran militia would've been). Based on that, I lean towards no.
On the other hand, there was a DSN episode in Season Six -- can't remember the title -- in which Benzar was in a verbal list of Federation worlds the Romulans had liberated from the Dominion.
Based on one serving as a Starfleet observer and another as quartermaster of a Starfleet surplus depot, I lean towards yes. (But then where were these "master strategists" when Starfleet was fighting the Borg and the Dominion?)
I see no reason to think there weren't Zakdorn strategists at work in the halls of Starfleet Command, coordinating Federation war efforts in numerous sectors.
In the novel A Time to Kill
, it's established that a Zakdorn named Koll Azernal was serving as Federation President Min Zife (of Bolarus)'s chief of staff and primary adviser. He is established to have been one of the key strategists behind many high-level Federation victories.