I've hunted in Botswana twice with Mark Kyriacou's Big Game and Bird Safaris, PH was Glen Munger. Each hunt was wonderful. Botswana is more expensive then Zim or Namibia but you will be in the unfenced bush and will have an experience more like the old time safaris. In terms of safety, I took my Sons on my second Safari and will take my Wife on my third, next year.
I personally would not go to Zim. I am sure that your PH would not put you in a danderous situation but with the Country unraveling your chances of having a problem are clearly greater.
I have no experience with Namibia but have only heard good reports from those who have hunted there.
I can only say GO! You will love it.
Terry