For the Greek god:
* HER-meez (with a long "E" sound like in "her" and a short "ee" sound like in "met").
For the brand:
* HER-mez (with a long "E" sound like in "her" and a short "eh" sound like in "met").
So, while the two are spelled the same, the pronunciation of the brand is slightly different from that of the god.