I had some problems which switching one of my chins to Mazuri. I tried switching him over in a two week period, and his crap got very runny and smelled quite terrible. I switched him back to his old food for a little while to let him get settled down. I then switched him very very very slowly to mazuri. It took over a month. He did well though and is no longer having problems.
However, diarrhea can be an indicator that something is majorly wrong. I was lucky in my case that it was just a food issue.