The firm also reduced its price target to $32 from $30 on shares of the Salt Lake City -based regional bank holding company.
Piper cited valuation as the stock is up about 30% from lows in July.
Additionally, shares now trade at a 10% premium to the peer group on forward earnings, the Fly noted.
Shares of Zions were higher in late-afternoon trading today.
Separately, TheStreet Ratings Team has a "Buy" rating with a score of B+ on the stock.
The company's strengths can be seen in multiple areas, such as its revenue growth, compelling growth in net income, solid stock price performance, impressive record of earnings per share growth and expanding profit margins.
The team believes its strengths outweigh the fact that the company shows weak operating cash flow.
Recently, TheStreet Ratings objectively rated this stock according to its "risk-adjusted" total return prospect over a 12-month investment horizon. Not based on the news in any given day, the rating may differ from Jim Cramer's view or that of this articles's author.
You can view the full analysis from the report here: ZION