The camera zoom on the DLs will lag slightly via DMX control as it is going through an internal serial interface. It will not behave the same as te zoom on a moving light for example.
Thats the only thing lagging. no cross fade. I use them at random to show people in the stands. so it has to happen pretty quick. they used to work fine.
Out of curiosity, how old are your units? Has anything changed recently in your system that might cause this? Might be worth a phone call to support at this point. +1 (800) 890-8989
Are you using the internal camera via SDI? If so, check the frame delay of that two fixtures. Because when you have a frame delay on the camera output plus the frame delay of the SDI input, the zoom of the camera seems to respond later or laggy.
I had this problem once, after a hard reset everything was fine.