First, let me tell you that I read what you previously said regarding this subject. With Planet Coaster there was the huge problem of degrading performance if you build many attractions, scenery or if you had many guests. This apparently even happend if you have a monster-PC. I hope that for Planet Zoo, Frontier finally starts to support Vulkan (or DX12) as the render API. Because the current problem with Planet coaster is that all the DX draw calls are done on one CPU-core, which is a limitation of DX11. This slows down the game enormously when you've build much in-game. I know DX12 is Windows 10-only (many people have Windows 10 now and support for Windows 7 will stop at the beginning of next year!). But you can keep DX11 AND DX12 at the same time, like many games do it now. But I would prefer Vulkan even more (but would probably be more work for you); it isn't OS-specific and makes it also possible to port any of your games to Linux, Switch etc. in the future.
Frontier doesn't do this yet, probably of the time and money this costs and because they don't want to exclude people by using an API their video card doesn't support. But come on, do you guys want to stick with DX11 forever with your nice COBRA-engine. It will hold your plans back severely as you have less headroom regarding performance. Switching to Vulkan or DX12 rederer will cost very much and makes programming games more of a hassle, but it will bring better performance when you've build much in your park as the draw calls could use multi-threading. I know that the calculations in-game are done on multiple cores, but the draw calls aren't.
Thus hopefully DX12 or Vulkan will be implemented into the COBRA-engine and used for Planet Zoo and all your future amazing games. It would be even more amazing if the developers from Frontier could then also implement/backport this in their older games, especially Planet Coaster (an amazing 2.0 update maybe?
). Then people can finally build the parks of their dreams. Or how NVidia would say it: the way it's meant to be played 
Keep the good work up Frontier Developments! It is so nice to see you recycling old ideas from games that you worked on (RCT3 and Zoo Tycoon) that were licensed for another publisher, improving it sooooo much and then releasing it yourselves.
Frontier doesn't do this yet, probably of the time and money this costs and because they don't want to exclude people by using an API their video card doesn't support. But come on, do you guys want to stick with DX11 forever with your nice COBRA-engine. It will hold your plans back severely as you have less headroom regarding performance. Switching to Vulkan or DX12 rederer will cost very much and makes programming games more of a hassle, but it will bring better performance when you've build much in your park as the draw calls could use multi-threading. I know that the calculations in-game are done on multiple cores, but the draw calls aren't.
Thus hopefully DX12 or Vulkan will be implemented into the COBRA-engine and used for Planet Zoo and all your future amazing games. It would be even more amazing if the developers from Frontier could then also implement/backport this in their older games, especially Planet Coaster (an amazing 2.0 update maybe?
Keep the good work up Frontier Developments! It is so nice to see you recycling old ideas from games that you worked on (RCT3 and Zoo Tycoon) that were licensed for another publisher, improving it sooooo much and then releasing it yourselves.