It doesn't just type jump from Poison to Water, it also jumps to Electric and Ground. Good luck~
...Okay but in all seriousness, yeah, this one is a team effort kind of deal. It's not impossible, though, just extremely sturdy.
Take advantage of its type jumping to the best of your ability, is my best advice. Physical attacks will also deal more damage to it than special ones, since it has lower Defense than Special Defense. The AI is also sometimes just dumb I mean really type jump to Poison against my Meowstic ZEL pls