With a fair, same-day weigh in, I definitely pick Zarate. With the shady help from Victor Conte and the early weigh-ins Nonito enjoys today, the size differential might be too much. But, Zarate is better than a guy like Nicholas Walters who beat Donaire handily.
This would have been a great fight but I think Zarate gives Donaire a thrashing after 6 exciting rounds. Zarate was even taller than Donaire with a longer reach and I don't think Donaire's left hook would be enough to deter Zarate, who has shown to have a good enough chin and recuperation as shown in his fight against Alfonso Zamora, who is arguably the hardest puncher of BW. Zarate, as stiff and robotic as he might look on film, is a much more skilled boxer than most people think. I think this would be similar to Donaire's fight with Walters. He was almost like Arguello stylistically. Very patient, poised, focused, accurate, doesn't waste a lot of punches, and slowly dissects the opponent with potent body attacks. Contrary to what many think about his punching power given his KO record he was more of an accumulation puncher who placed his shots very well, but still punched hard enough to be able to knock opponents out with one punch.
Walters was also massive and Donaire was out of his weight class...no shame getting flattened by walters
That's the first thing I thought of when I first watched Zarate. He and Arguello are perfect examples of textbook boxer-punchers. I even made a thread about Zarate and Arguello years ago. https://www.boxingforum24.com/threads/better-boxer-puncher-alexis-arguello-or-carlos-zarate.340190/
Here’s another impressive showing by Zarate. He was really good at cutting off the ring, didn't rush at his opponents or get sloppy, had great boxing IQ and good footwork to go along with his great offensive skills and power. He did the basics very well. This content is protected
He was a total monster in the ring. A fearsome puncher with insane height and reach for the weight class.