AMENDMENT TO THE TRUST AGREEMENT Establishing the ZIONS BANCORPORATION DEFERRED COMPENSATION PLANS TRUST

EXHIBIT 10.12

AMENDMENT TO THE TRUST AGREEMENT

Establishing the

ZIONS BANCORPORATION DEFERRED COMPENSATION PLANS TRUST

WHEREAS, effective October 1, 2002, the Zions Bancorporation Deferred Compensation Plan Trust (hereinafter called the “Trust”) was established by and between Zions Bancorporation (hereinafter called the “Employer”), and CIGNA Bank & Trust Company, FSB, a federal savings bank with its principal office and place of business in the City of Hartford, Connecticut; in connection with and as part of the Zions Bancorporation Deferred Compensation Plan (hereinafter called the “Plan”); and

WHEREAS, effective April 1, 2004, in connection with the sale of CIGNA’s retirement business to Prudential Financial, Inc., CIGNA Bank & Trust Company, FSB merged with another banking institution owned by Prudential Financial, Inc. to form Prudential Bank & Trust, FSB (hereinafter called the “Trustee”); and

WHEREAS, effective December 31, 2004, the Employer wishes to amend the Trust Agreement and create a Schedule of Covered Plans (Exhibit A of the Trust Agreement) to include in the Trust additional plans the Employer has added under its Group Annuity Contract as a result of non-qualified deferred compensation legislative changes;

NOW THEREFORE, the Trust Agreement is hereby amended effective April 1, 2004 as follows:

NOW THEREFORE, the Trust Agreement is hereby amended effective December 31, 2004 as follows:

IN WITNESS WHEREOF, this amendment has been executed on the dates indicated below.

EXHIBIT A

SCHEDULE OF COVERED PLANS