Definitely a good operating system that has very good compatibility (in my experiences) is Windows XP. I was able to play games like Red Alert Two with absolutely no problems. Considering Roller Coaster Tycoon was released about only one year before to RA2, I can safely say that Windows XP supports it. As for Zoo tycoon, Windows XP was released in April of 2001, while Zoo Tycoon was released in October of the same year, so compatibility will definitely be great for that one.
Ok, now that I have pointed you to the operating system you should use, you next goal would be trying to find hardware that games like that support, and the operating system itself supports. Now, I had an uncle who had a perfect, and I mean perfect link between modern computing and older retro games. I cant remember what exactly the system it was, but I do remember that it used DDR2 RAM, a BFG nvidia geforce 8600 gt, and this motherboard:
https://www.newegg.com/Product/Product.aspx?Item=N82E16813128048&nm_mc=AFC-C8Junction&cm_mmc=AFC-C8Junction-_-na-_-na-_-na&cm_sp=&AID=11552995&PID=6361382&SID=tomshardware-2335077689499532604It was reasonably fast and did not have any problems even by today's standards, and I regret taking it apart and trashing the motherboard because it did not pick up any of my keystrokes. That was a while back when I was 13 and just starting out with computers. If only I would've known.
Anyways! I hope that you find yourself a computer that fits your needs. It doesn't have to be what I told you but, when it comes to gaming, Windows XP is a good option, because if you need to use it to look something up really quick online, you can still do that.
Best of luck,
Anthony
