Well, the first thing that comes to mind when you want a CTF and KOTH maps, is a TF2 maps. They're all already has areas for team spawns and points or flags.
You can also use a Control Point, Payload and etc. maps if you have the idea of where to put flags and points, but not with splitted areas ones.

You can also use a Counter-Strike or Half-Life Deathmatch maps, but for me they are small for Zetas.

So i find a TF2 NAVMESH Pack that gonna fun with CTF And KOTH Map

i have use KOTH in rp_downtown_v2 and gm_fork