Euro zone factory growth was weaker than previously thought last month as the bloc’s core countries continued to struggle, a survey of businesses showed on Monday. To restore economic growth and combat deflation, the ECB started buying around 60 billion euros a month of mainly government bonds in March and the survey suggested it is having at least some effect. Markit’s final May manufacturing Purchasing Managers’ Index (PMI) was 52.2, below a preliminary flash reading of 52.3 but just ahead of April’s 52.0.