Its a KF.
I'm not too sure of the extra letters for the particular engine that is in our cars though (ie, -ZE, -DE, etc). I think the Eunos 500s have the KF-ZE in them as I think theirs is a more tuned up version. (don't know where I got that from so can't back it up but I've always thought that was the case).
KL = 2.5L (MX-6, 626, Probe, Telstar V6)
KF = 2.0L (AstinaV6, Eunos 500)
K8 = 1.8L (Eunos 30X)
There's some interesting info on the Mazda K series V6 engines
here. Hope this helps.