Nope, it’s not possible. You would have to make an alternate version of your Z and substitute via the calt OT feature.
Is there a way to position just some nodes of a glyph with Opentype? If yes how do I do it?
I would like to make contextual alternates this way. Like for T|Z make the top of Z shorter so it fits better. This way I could avoid generating many calt versions and keep my design simple.
Sorry if this has been discussed previously. Thanks for your help!