Since Zubat are part poison, they should recieve bad damage from psychic attacks.
In Union Cave in Johto, the zubats doesn't recieve "bad damage". They do not take super-effective hits from psychic attacks. I don't know about other locations.
It's difficult to build a strong team against most types is the game is broken like that.
Please look into it, and i will check here if there is any answers to this topic.
I tried to get a screenshot of the game NOT giving me the message of psywave being super-effective, but yeah...
Maybe i missed something in the game mechanics, but i sure hope not, because that would make me look very stupid.