Pillsbury Winthrop Shaw Pittman has followed its high-profile role on the $18bn (£9.57bn) bid battle for Unocal, with a role on Zions Bancorporation’s $1.7bn (£970m) takeover of Amegy Bancorporation.

The deal sees the Salt Lake City-based financial services group acquire Texas-based Amegy, the largest independent bank in Houston and the third-largest independent commercial bank in Texas.