Irish Power: Rory McIlroy and Shane Lowry among leading teams at Zurich Classic

The Irish duo opened with four-straight birdies en route to carding an 11-under 61 in Four-ball play on Thursday.

McIlroy said he and Lowry were feeling the pressure a bit after seeing some of the low scores ahead of them.

"You know that you sort of need to get off to a good start, and thankfully we did. We were 4-under through four, which was really nice to see, and from there you've got some momentum and you're just trying to keep it going," he said

"But for the most part today, we kept both balls in play. We were having two looks basically on every hole at birdie, and that's the way you need to play better ball. Everyone thinks it's maybe a bit more gung ho than that, but as long as you have two balls in play off the tee, two balls on the green, I think you're always going to do pretty well in this format," he added.

Speaking after the round, Lowry said: "We both played nice golf.

"We both made some nice birdies and contributed to the team, and I think we're very happy with the day."

They are joined at the top of the leaderboard by the pairings of Ryan Brehm-Mark Hubbard, Ben Kohles-Patton Kizzire and Aaron Rai-David Lipsky.

England's Rai and his American partner put together a bogey-free round which featured 11 birdies.

McIlroy previously said that he had approached Lowry about teaming up for this year's edition of the PGA Tour's only team event, having previously resisted repeated overtures from two-time Masters champion Bubba Watson.

"I don't know if I knew what to expect. I've watched this tournament a little bit over the years on TV, heard some good things from some of the players. It's nice to come here, team up with a really good friend, and if we play a good round tomorrow, it'll be awesome to be in contention for the weekend and try to get a win on the PGA TOUR with a friend beside me. Looking forward to it," the Northern Irishman added.