I am no expert in zonata in anyway, but I have successfully been keeping a rather large Kern county intergrade Z in a similar setup you proposed for a few years now. It is in a glass tank with cypress mulch as bedding, with an underpad heater that gets a warm spot at around 79F or so. I am not too much of a stickler when it comes to temperatures, but I have found it has worked well. Air temp in my room is rather cold, around the low to mid 60s due to living in the San Francisco coastline.
I have a "leveled" structure of cork bark that allows the snake to either rest on the floor of the cage where the heat pad is, or to escape "upward" to another "level" of cork bark where it can get cooler (essentially, the reverse of how they would do it in the wild, underground to cool off, higher up in the rock outcrops to bask). I have found that the snake utilizes this alot. On some days, I turn off the heatpad and turn on a 50W bulb, and observe the snake going up to the higher levels of the cork levels to bask, then back to the bottom to thermoregulate.
Zonata like thier humid hides. I have a section of the tank that is devoted to moist sphagnum moss (true sphagnum, I hate "green moss", such garbage). I cover the section with a large piece of cork bark and will often find the snake underneath the bark, ontop of the moss. Usually there while inshed, as well as just to hang out.
Zonata are very interesting snakes, but they are snakes. As long as there are OPTIONS in their habitat/enclosure, like they would have in the wild, I am sure they will do fine for you. I have herped for Coast zonata in their natural habitat within the Bay Area (San Mateo, Santa Clara, and Santa Cruz counties)and can tell you that the temperatures and climtae varies greatly during the year and seasons. Keeping up with the diversity of temps, etc seems like a good bet.
