Pronounciation of TH+S

I've never heard anything but the ess sound rather than the zee sound after TH. Anyone else?

The S is voiced (zz) if the TH is voiced. The S is not if the TH is not.

Human beings are lazy speakers (in any language), and it is easier to use the same voicing. It is also easier to change the voicing in some cases, and this tendency even influences our spelling, so wolf>>wolves. Since we don't use DH in English for the voiced version of TH (somewhere in the transition from Old English to Middle English, we gave up some perfectly useful letters to indicate these, though Icelandic retains them), we don't change the spelling mouth>>mouths, even though we say "moudhz"

Dear Adam
The kind of D you are talking about I guess have nothing to do with the sound of TH in English. Because I do believe the TH stuff comes from Indo-European roots. i.e. Mithra in Indian. It sounds like Arabic TH. i.e. tholth= 1 third.
The so-called "soft D" in the Norse languages sound more like L while tongue touches the lower front teeth. i.e. gade= street in Danish. I say that from my experience, that lots of foreigners pronounce the soft D as an L when speaking Danish. Danish doesn't have a letter for it

Hope you don't think me too pedantic but you have stumbled on the definitive pronunciation irony: i.e. that the word "pronunciation" is so often mis-pronounced "Pronounciation" and therefore mis-spelt as well - as you show so effectively!
I guess this deserves a thread all of its own...