You can tell that the action live Rangers sequence is done by stuntmen because in the command center scenes when Zack is helmet less you can see that his left hand with his glove on is with the 4 fingers because of Walter Jones not having a middle finger. The live American action footage black ranger fighting has 5 fingers on the left hand.
When piranhahead monster comes to fight after the putty fight it's live with ranger then as soon as the zords come in it's get switched to zyu/Japanese footage the at some moments to goes back and forth between both.