The moment resurrection is casted, dead units that are revived still have 0 hp, so you can wait 0 seconds (use a timer) and compare the hp to the hp before. Every unit that has now > 0 hp and was at 0 hp before was resurrected.
I do not know if it needs to be MUI, because it is practically impossible, that two units cast at the same time, so a global timer + global group should be enough.
You need to make sure, that no other trigger increases the hp of dead units (in general you should never increase hp of dead units, as then functions like IsUnitAlive would return wrong results).