Well, I've got both the Touch 2G with a very good line out cable (not a cheap dock/dongle) and the Zune80, and I can say unequivocally that with the T4, at least, the Zune HP and an amp (with a good mini to mini cable) sounds as good as the Touch LOD, head to head.
Without the amp, the Zune HP outperforms, to my ears, the Touch and my old iPod 5.5g HP out (no EQ on either). Just because the Zune isn't selling more units doesn't mean it isn't being used by discerning listeners.
So I'd say the Zune HP out offers better SQ than any iPod HP outs, though the Touch is pretty close. I would not necessarily agree that the Zune doesn't need an LOD since its HP out is so good, and I'd love to have a portable Zune LOD.
But, when I use the Zune in its AV cradle as the source with my Class D amp and vintage KLH speakers, the sounds are just as crisp, clean and ear-pleasing as my CD player. That does say something about the Zune, in my view. When in the cradle, the Zune audio controls are still functional, which may indicate it's not an LOD at all, but merely the HP out coming from a different place (the bottom and not the top).