Since there are now quests like 'kill 50 parasol zombies' it would certainly be useful to know not only in which levels a particular zombie appears but how many of them appear in that level (when it is predictable) or at least a range. Alternatively, it would be nice to have a list of which level offers the maximum number of a particular zombie; e.g. Pirate Seas day 20 has, by far, the most seagull zombies, so that is the best level for the seagull quest.
For example, I think Dark Ages Night 7 has 5 knight zombies.