Best Coin Farming Method

hello, a few weeks ago i decided that it could be fun to complete all the achievements on the game (first one).
I'm a mobile player, so i have to do 46 achievements, which i think 7 of them require to have the endless last stand, vasebreaker, "I, zombie", which all cost 400k in total and I wanna know what is the best method to farm coins because i'm actually using the last stand one with all margarets and, after doing some math, i am getting around 50k/h, which is not very much. Also, there is an achievement that requieres to get all the different types of plants in the zen garden, which is also a lot of money.

I need help pls if someone knows a good method tell me, i will be very grateful.