Sterilize the entire galaxy, or at least everything that has any trace of psychic presence/emotion, and then yourself.
Wait an indeterminate period.
They will run out of gas and die with a whimper rather than a bang.
You have to get EVERYTHING though.
This also assumes that they don't meddle and make life occur solely for the purpose of worshiping them.
They might manage to secret some bionts or bacteria in a crevice you missed, or skip that by millions of years and have much more evolved things.
So practically speaking, no. They are quite powerful to begin with and in practice, you wouldn't elude their attention at all and they would stop you before you got any real distance. Your very scheme would inherently be known to Tzeentch, and the others to the extent they were aware of it, wouldn't like it, even though Khorne hates everything, he's addicted to hate. He can't stop hating things, etc.
Even if it somehow worked they'd probably find a way to say "Hi" to Nids' or some other form of outsider, or meddle with mechanical things as a way to get a foot hold, etc. (They can infect inanimate objects after all. I'm assuming they have the expertise/inherent abilities to get life a going with a demonic infection. Nurgle could, however ruefully, create life that wasn't totally preferable to him so later, him/everyone had more Life to worship, etc.By
sending a plague demon with bacteria to start life, etc.)