How to render animated object with shadow only


Hello, guys can you please help me to solve my problem.

I have animated curtains and plant in my sceen and i want to render them without the need to re-render the all interior. do you have any solutions for this?

3ds max 2016, corona-render 1.7. i have tried to use shadowcatcher material but it works not as i expected or i did wrong setup of material… i just assin shadowcatcher

material on all my sceen exept the curtains and plant and in sceen enviroment tab i have next setup

with this setup i have 2 hours render per frame 2000x1000px (i need 400 and in 4k resolution). help please! thanks