Sorry for the month late reply.
You'll need the Prototype style modtools for making a prototype style map. Here is zombiemodding.com's download:
https://mega.nz/file/ZMciRLpD#fdQankgzoj9E0qcif4QpzxezYA0d36cGIvUuDllh1ywMaking a prototype map is almost exactly the same as making a DLC3/1.4 map. The only difference is that zombie spawn mechanics are slightly different.
Basically, there are no zones.
In Radiant, the zombies for the starting room zombie spawners need the following KVP:
targetname / zombie_spawner_init
These zombie spawners will be activated at the start of the game, hence the 'init' meaning initial.
Next, if you have any doors that lead into rooms with new zombie spawners you must:
1. Select the door (the actual door, not the trigger)
2. Select the zombie spawner(s)
3. Press 'W' on your keyboard.
Now, when that door is opened, it will activate the zombie spawners in that room for the rest of the game.
Unfortunately this means that there is no logic in determining where the zombies will spawn. They spawn randomly from every active spawner.
This shouldn't be too much of a problem if you don't plan on making a huge map however.
Sorry if this wasn't the best explanation, but I hope I've helped a little bit.