Kafka and Zookeeper stable release

[Nancy Feng (defeng)]

Hi, I’m upgrading cloud infrastructure kafka(2.3.0) and zookeeper(3.4.9) to 
newer version. May I ask recommendation of the best latest stable versions for 
the both I could use?

Kafka 2.6.0 or 2.5.1?
How about compatible zookeeper version?

Thanks,
Nancy