[link to original on tumblr]
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In the Miracles' version, the third line of every verse starts with "Though." "Though you treat me badly," "Though you do me wrong now," and "Though I wanna split now." In the Zombies' version, instead of that melisma'd "though," it's "Oh ho ho."
In looking into that difference, I've discovered that the Zombies substitute the Miracles" third verse ("I wanna leave you, don't wanna stay here / Don't wanna spend another day here") for the second ("Baby, I don't want you, but I need you / Don't wanna kiss you, but I need to"). They also transpose some lines (and add a word), so that the Miracles' "Though I wanna split now / I can't quit now" becomes "Ho ho ho, I wanna quit now / I just can't split now."
I looked up "You've Really Got a Hold on Me" on Wikipedia (just to confirm that it was written by Smokey Robinson), and I discovered that he wrote it with Sam Cooke's "Bring It on Home to Me" in mind. Normally, I'd be wary of Wikipedia's veracity, but there's a citation that leads to a digital book that says:
The Miracles returned to the pinnacle of the R&B hit parade for the second time at year's end with a passionate "You've Really Got A Hold On Me" that cracked the pop Top Ten. Smokey, who wrote and produced this one all by his lonesome, found his muse in Sam Cooke's then-current hit "Bring It On Home To Me." "Sam had that record out at the time," he said. "I was in New York taking care of some business for Berry for the company with another publisher. And I wanted to write something like 'Bring It On Home To Me.' I was in my hotel room with nothing to do, so that's what I did, 'You've Really Got A Hold On Me.'"According to the Zombie Heaven liner notes, the Zombies medley'd these two because that's what the Miracles did on a live album. I don't know if the Zombies knew that "Bring It on Home to Me" inspired "You're Really Got a Hold on Me" though.
I suppose if the Zombies followed a live version (which I haven't heard) maybe it's that live version that deviates from the studio version. And all the changes I noted above don't really apply.