Receiver Route Adjustments versus Zone or Man Defence

One of the rules that I have adopted and it's easy to remember is: "Run away" from man and "Sit down" versus zone coverage. In other words, when adjusting football passing patterns versus a man coverage system, call crossing patterns or passing routes whereby your wide receiver is running away from the defensive back. Look for the mismatches where your wide receiver is basically a better athlete than the defender and is out running them. A lot of teams when up against a man coverage football system will isolate their best athlete versus a weaker defender and let his athletic ability get him open.
Versus zone coverage, the adjustment to make would be to get your players to "sit down" or stop and set up in the seams between the zones. Basically your wide receiver would run his route and look for the opening between zones, stop, set-up, while the quarterback would scan and find him open in the seams.

The key to all your football systems depend a large amount on your personnel that you have to run them. Based on that, you design or adopt a particular football system that your players have the means to thrive in. In other words you don't run a system that your players don't have the tools to operate.
Once you establish that system and your players thrive within it you will be able to make game adjustments within that football system that will be easy for players to adopt. One of the things that you will probably do at some point is to adjust your passing patterns based on what kind of football pass defence that you are up against whether it be man or zone defence.

Rule of thumb: Run away from man and sit down versus zone!

Cheers!