If you are going to do an Oly lift variation, snatch/clean on DL/SQ day, do them before. I cannot explain the reason why; however I have a friend who is an Olympic weightlifter who told me to always do explosive lifts first. Also, I know from personal experience that my legs are too fried after SQ and DL to have any leg drive left for an Oly lift pull variation.
What kind of plyometric exercises do you want to add? Lower body, upper body, box jumps, plyometric push-ups, etc..?
I used to do box jumps, standing broad jumps, or jump squats hours after I SQ or DL when I was fresh. I took that amount of time in between because my goal at the time was to increase my box jump height, standing broad jump distance, and jump squat reps significantly.
If I did low box jumps for conditioning, I would do them right after my weightlifting session.
It depends on what your goals are with plyometric exercises.
Edit: I had edited this post around 1pm, but a glitch in the system did not make the changes.