the habitable zone isn't actually in the green part of the zone
Dude, I've put way too many of my habitable planets near the outer edge of the green zone, and yes, by habitable I mean covered with some of that nice liquid water stuff.
The habitable zone just provides a baseline as to where habitable planets are likely to be found, in reality you need an atmosphere to hold onto water and up the temperature so that the water turns into a liquid.
In fact, you can make atmospheres thick enough to provide enough warmth outside the habitable zone, like Venus.
Venus would actually need to be at around Jupiter's orbit to be habitable-
ish. I say that because you'd still have the deadly, crushing atmosphere blocking your way.