Sizing Europe is reported to be in tip-top shape as he bids to retain his crown in the sportingbet.com Queen Mother Champion Chase at Cheltenham on Wednesday.
The 10-year-old has a tremendous record at the Prestbury Park track, having won the Arkle Trophy in 2010.
He has a good season so far, winning the Tingle Creek Chase at Sandown in December and the Tied Cottage Chase at Punchestown last month.
"He's in good form. Everything's gone OK so far, so we're happy enough," said trainer Henry de Bromhead.
"He's travelled over well and the ground looks OK.
"He's won an Arkle and this race so we're hoping he can run another big race."
His regular partner Andrew Lynch is oozing confidence ahead of Sizing Europe's attempt to land back-to-back victories in the two-mile championship.
"I can't wait to ride him. He's been in fabulous form this season, winning three from four. If everything goes well, he should take a lot of beating," said the jockey.
"He was impressive the last day. He was in good form after winning the Tingle Creek and Henry said 'go and enjoy yourself, get him jumping and have fun'.
"He's in good form, worked well the other day and is one to look forward to."
Big Zeb will try to win back the crown he lifted in 2010 and turn the tables on Sizing Europe from 12 months ago, when he was beaten five lengths.
Although Colm Murphy's stable star got his revenge at Punchestown in May, he was 15 lengths adrift of his old rival when they last met at Punchestown.
"He's very good, not a bother on him. He travelled over on Monday night," said Murphy.
"We're hoping for a better run than last time. He seems in good nick, so we think he can run a big race. We'll be hoping for the best."
Realt Dubh has not run since Punchestown's May Festival, but trainer Noel Meade is happy to go for this race rather than wait for the Ryanair Chase on Thursday.
"He's worked great and he does run well fresh," said Meade.
"We're basically going for the Champion Chase because the Ryanair looked more competitive in that there's likely to more runners and there's probably six or eight horses with not a lot between them.
"We felt that we had a better chance of being in the money in the Champion Chase, so we'll see what happens.
"There will be a lot of horses fancied in the Ryanair, so we're happy enough to go in the other race and take our chance."