What's the difference between these words?
I know both are used when someone deserves high respect, but is there any other difference between 드시다 and 잡수시다?

Question

Answer

잡수시다 is honorific expression(높임말) of 잡수다
잡수다 is honorific expression(높임말) of 먹다

드시다 is honorific expression(높임말) of 들다
들다 is honorific expression(높임말) of 음식을 먹거나 마시다.

Thus, 
잡수시다 honorific expression(높임말) of 먹다
드시다 is honorific expression(높임말) of 먹다 and 마시다.

잡수시다 is used for food.
드시다 is used for food or beverage.