Why is it important to zero beat?
So the two (or more) stations are on the SAME frequency.
I have a kenwood 590 and it's delightfully good at rapid zero beating. There is nothing more impressive then seeing a number of stations QSO all within a few hz of each other. Really makes it ez to listen to as my filters are pretty steep.
Please, PLEASE don't try on purpose to be exactly on the same frequency as OTHER stations that are CALLING someone !!! Is this meant to be a joke?? Really??
Anyone that has ever been DX, or has activated a WWFF / POTA park on CW (and that is now hundreds of people every week!) will tell you they do NOT want two stations on the same frequency calling them. That just turns into one solid tone. Being at least 50 Hz off the CWing station is much better than using that evil DSP function on newer radios that matches their freq exactly. 70 or 100 Hz off is even better.
I can't count how many times I have been at a park this summer and had to just listen to 2 or 3 signals exactly zerobeat that turned into one long tone, what a waste of time, theirs and mine. Then if I get one or two letters clear at the end of the mess and I ask for that partial call, both (or more) call again, OK, I won't even start on THAT rant. THAT bad practice is becoming very prevalent, but that's another topic.
So please don't use the Zerobeat function on DX or park stations with a chance of more than one station calling, please. That is NOT a joy to listen to....
Glenn AE0Q