Multiple machines work on different parts from a moving tray?

I have a challenge that I’m not sure how to approach. I’ve made an illustration of what I want to achieve:


There is a tray carrying objects, moving past four machines. Two cleaners and two inspectors. Each machine work on a single object at a time and work their way from left to right. The machines must pick parts from fixed positions; it’s the parts positions that must change by moving the tray one increment to the left. Cleaner 1 and Inspector 1 works on the last half, while Cleaner 2 and Inspector 2 works on the foremost half simultaneously.

I’m looking for ideas on how to best approach this.