UPDATE guys: I was able to make a batch file to do exactly this
Obviously replace the directory with yours, and make sure to place the bat file the same folder as ZClient.exe
It runs ZClient.exe alone first then waits for 15 seconds for you to autologin. after 15 seconds it will try to do the "drag and drop" maneuver to run D2R.exe, it checks for it three times at 5 second intervals just to be sure, then closes itself. If your computer is too slow to open Zclient or login, you can extend the delay. for example 1000 seconds = ping 127.0.0.1 -n 1000 -w 1000 > NUL