Nowadays you can unzip on a mac, and sit on a pc. Daz gives indeed exe files for winPC and sit files for mac users. You cannot use mac on pc or vv as mac files have "forks" in which they keep additional info. On pc poser files, this info is stored in so-called "rsr" files.

I have tried prudent planning long enough. From now I'll be mad. (Rumi)