I see, thanks for letting me know! I didn't know Zen Mode was ever that punishing. If a level in Zen Mode ever requires 400 points in 1:10, that does sound unusually high - maybe even a bug. Do you remember which level it was? That'd help me look into it.
Thanks that's indeed a bug -- Zen Mode is supposed to make the game easier by making levels shorter. But on levels like this one with a score requirement, it makes it much harder to make the requirement!
I'll think of a way to fix it, probably by lowering the level requirements in Zen Mode too -- so that you'll only need around $100-$150 instead of $400. Thanks for reporting the issue, sorry for the trouble!