I see from social media that a former colleague "A" (whom I'm not close to and haven't spoken to in years) now has a differently-gendered name, look, and pronouns from what they had when I and other colleagues (B, C and D) worked with them. Because A was an exemplary and memorable co-worker I do sometimes find it useful to refer back to them, their approach and their work when talking with B, C and D. But whereas I just happen to have noticed that A's name and pronouns have changed, I have no idea whether B/C/D know this or to what extent they're still in contact with A.
What's the best way of referring to A in conversation with the others? If this were just the cousin James I grew up with who now prefers Jimmy, I would have no qualms about referring to "James" among family members who still think of him that way. But when it comes to gender identity, I hear that "dead-naming" someone in their presence can be hurtful—from that, I extrapolate that the ethical course is to encourage, with as little fuss as possible, the habit of also using a person's preferred names and pronouns in their absence. This is easily done in the case of famous people: I can say Caitlyn Jenner won an Olympic medal, Chelsea Manning leaked military secrets, or Elliot Page played Ariadne in Inception, and most people will know enough to join the dots. The difference here is that A's identity change may not be known to the people I'm talking to, so they'll possibly not know who I'm talking about. The least-worst formulation I can think of is "that project completed by A (whom we knew at the time as Z) Smith". Is that good? I'm asking this question here because any formulation I can think of, including that one, seems problematic in one way or another: aside from sheer unwieldiness, I'm unsure how to tread the line between dead-naming a person behind their back, and drawing too much attention away from the topic at hand and onto identity issues (possibly even eliciting irrelevant and unwelcome judgments on the latter from B/C/D).
I haven't communicated directly with A in a long time, and I'd say their gender identity is among the least interesting/relevant reasons for breaking radio silence, or topics to talk about if I did. So I don't see it as A's role to advise or educate me on this (though I'm willing to be corrected on that point too). And I don't know anyone else who (to my knowledge) has an inside perspective on this issue.
In response to the comment about goal-setting: my main goal is to communicate as clearly as possible about the work-related topic without getting sidetracked. To that end, if there weren't an ethical problem with using the old name I would simply use it. In analogous situations where there's a last-name change, e.g. due to marriage, I use whichever name I think my interlocutors will recognize most readily, and I feel free to do that because using the old name doesn't hurt anyone (except in rare situations that I'm happy to rely on my own judgment to identify, and where I'm comfortable with the consequences of a well-intentioned error). But name/pronoun changes associated with gender identity strike me as requiring more careful handling, and most people including myself are still uncertain of the rules. Taking that into account, the goal then becomes: with as little fuss/disruption as possible to the conversation, model for others a communication style most likely to foster non-discriminatory collective handling of identity issues.