By Shreyashi Sanyal and Shristi Achar A May 8 (Reuters) - Wall Street's main indexes were flat on Monday as bleak earnings from companies including Tyson Foods and Catalent clouded a rebound in regional lenders ahead of a key inflation reading this week. Peers Western Alliance Bancorp WAL.N and Zions Bancorp ZION.O rose 3.9% and 3.2% respectively. Tyson Foods TSN.N dropped 12.3% on posting a surprise second-quarter loss and cutting its full-year revenue forecast, as prices for its beef and pork declined.