Zions Bancorp. reported net income of $6.7 million or $1.13 per share in the first quarter of 1991, an 11.9 percent increase over the $6 million net income or $1.01 per share in the same quarter a year ago.

Harris H. Simmons, president, said the pre-tax earnings for the first quarter of 1991 were $10.4 million, a 29.7 percent increase over the $8 million earned in the same quarter in 1990. The company's return on average shareholders' equity in the first quarter was 14.82 percent.Simmons said the improved earnings in the first quarter were the result of a 16.7 percent increase in the company's taxable/equivalent net interest income.

He said the higher level of net interest income results from a 19.2 percent increase in average earning assets totaling $3.1 billion in the first quarter compared to $2.6 billion a year ago. He said the increase in earning assets was achieved predominately in the company's money market investment and securities portfolios.