Summon Mobs In Certain Location

[RelevantCost]

I'm fairly new to Skript and I was wondering how to continuously summon mobs in certain areas, with a mob cap and time between spawns as well. I am trying to do something like the mobs that spawn in Hypixel Skyblock, like the zombies in the forest. Please let me know how I can do this.

Thanks

 

[UltraGamesNL_YT]

command /summonmob <text> "<text>"
  permission: mob.spawn
  permission message: &cLet's not.
  usage: &c/summonmob <mob> <x, y, z>
  aliases: /sm
  trigger:
    execute console command "/summon %arg-1% %arg-2%"
    send "&aSuccesfully summoned mob &2%arg-1% &aat: &2%arg-2%&a!"

didn't test it but im sure it works if you note argument 2 like this: example "21 4 66" with the quotes ("")