like herding cats

(It's) like herding cats
This expression refers to the difficulty of coordinating a situation which
involves people who all want to act independently.

Example: Organizing an outing for a group of teenagers / people from different countries is like herding cats!

(It's) like nailing jelly to the wall
To say that something is like nailing jelly to the wall, you mean that it is extremely difficult to do, if not impossible.
(невозможно;
≈ так же трудно, как поймать/прикнопить солнечный зайчик)

Example: Keeping track of his movements is like nailing jelly to the wall.

Example: Writing the history of this period is like nailing jelly to the wall. (trying to give exact details for something that it is not possible to know about exactly)

see
[решетом воду носить]