THEIR last three meetings have been titanic battles but tomorrow's renewal of the Queen Mother Champion Chase should finally prove who is the two-mile chase king of these islands.
Sizing Europe took the racing world by storm in 2011 when he demolished a high-class field, leading home an Irish 1-2-3-4 with Big Zeb trailing in five lengths behind Henry de Bromhead's star.
Big Zeb gained revenge at Punchestown but since then Sizing Europe has shot himself to the top of the betting market with astounding performances in the Tingle Creek and Tied Cottage chase at Punchestown, where he again got the better of Big Zeb, but De Bromhead thinks it will be much closer this time around.
"I don't think conditions suited Big Zeb that day, it should be another great battle," he told the Herald.
"He's in great form, I'm delighted with him. He's an amazing horse to be associated with, a horse of a lifetime.
"I don't know if he's a better horse than last year, Big Zeb wasn't at the top of his game last time out, but he's as good as he was this time last year.
"Our last workout on the Curragh went very well and we're all systems go.
"It should be another good battle with Big Zeb and I wouldn't rule out Finian's Rainbow either."
If Colm Murphy's gelding is to turn the tables on his great rival he will be praying for sun, sun and more sun.
"Our horse is as good as we've ever had him going to Cheltenham. He's in really good nick.
"All we need now is for the watering to break down over there!" he said. "As long as it is good ground we would be happy.
"But, with Big Zeb, it's really a case of the faster the ground the better. And that might not suit some of the others."
Cheltenham officials still hope to start the Festival with ground on the slow side of good, with watering continuing to take place.
The surface at Prestbury Park is good, good to firm in places on both the chase and hurdles courses.
Murphy has admitted that he has had to limit the work Big Zeb has done at home because of the horse continuing to suffer from arthritis, but he is confident he remains in top shape.
There is a third Irish challenger in the shape of the Noel Meade-trained Realt Dubh, who was third in last year's Arkle.
Heading the home brigade is the Nicky Henderson-trained Finian's Rainbow, runner-up in last year's Arkle.
Completing the line-up are Gauvain, I'm So Lucky, Kauto Stone and Wishfull Thinking.