Wikipedia cites Hinge (2001) as reporting the claim that Cretan Greek had [s] as an allophone of /ts/ after a nasal. I’m not a German speaker so I can’t verify this.
The relevant section from the Wikipedia page for Zeta is quoted below (as viewed on the 30th of January 2024)
- ν disappears before ζ like before σ(σ), στ: e.g. *πλάνζω > πλᾰ́ζω, *σύνζυγος > σύζυγος, *συνστέλλω > σῠστέλλω. Contra: ν may have disappeared before /dz/ if one accepts that it had the allophone [z] in that position like /ts/ had the allophone [s]: cf. Cretan ἴαττα ~ ἀποδίδονσα (Hinge).
Citing: Hinge, George. “Die Aussprache des griechischen Zeta”, in Die Sprache Alkmans: Textgeschichte und Sprachgeschichte. PhD dissertation. Aarhus: Aarhus University Press, 2001, pp. 212–234 = [1]
I’m really looking for an English translation of Hinge 2001 so I can verify that it does indeed claim this fact.
/ts/
and then running those paragraphs through google translate (the fact this is generally more useful that relying on my own translation, shows how far I am from fluent, hence why this is not an answer), it appears that the /ts/ phoneme being discussed is the Proto-Greek /ts/ < first palatalisation of *ty or *tʰy, claiming the earlier [ts] sound of this phoneme persisted late in Cretan, as it was spelt <ζ> in the archaic period and later with <ττ> or <θθ>