The research house said Threadneedle's investment team was highly experienced, with excellent research and risk management processes.
"Zenith is very impressed with the calibre of Threadneedle's specialist global equity team, who have an average of 16 years' experience in investments," Zenith said in a report.
"We believe that this depth and breadth of experience forms the basis for Threadneedle's high-quality research, which directly flows into stock selection."
