Hi Liz - I am north of you in Indy, so slightly colder winters, but otherwise similar climates. I have had Zia queens in the past and just installed three more. I love them. They are hardy, know how to make a honey crop, easy to work and I suspect they also handle varroa better than most. In my opinion you can't go wrong with adding them to your yard. With that said, I would not requeen a normal size hive. I made that costly mistake in the past. I would put them in nucs and overwinter them in the nucs, or requeen your hives with them using the entire nuc once they had a chance to build a strong five frame nuc. I found by removing the old queen from a hive and introducing the new queen in her queen cage didn't work for me at all. They release her ok, but it seems as if the neq queen can't get to egg laying speed fast enough for such a big hive that they perceive her as failing or defective and promptly supercede her. I found t safer to get her started in a nuc, let her fill the nuc to a strong size and than requeen the hive with the nuc unit. And as I sai, the other option would be to overwinter them in the nuc, I have done that myself and had no problems with it. I had a very strong nuc in the spring to replace dead-outs way before any nucs were available to buy from the south. Zia queens get my two thumbs up. Not to mention that Melanie at Zia queen is super nice to deal with.
Good luck, Liz.