Steps to Reproduce

http://zkfiddle.org/sample/25d4ve3/1-ZK-4282
Select some items in model 1 and model 2

Current Result

When selecting any items, the listboxes using the same model is not synchronized.
Only when some actions like changing page number.

Expected Result

When selecting any items, the listboxes using the same model should be synchronized.

Debug Information

The parent class of SimpleGroupsModel is AbstractGroupsModel, which is supported selection since ZK 6.0
https://github.com/zkoss/zk/commit/43a9d78293848afcd06cbde27043edc850e889d3

The onSelect event is deferred by ZK. so it might be sent until next AU request.

Workaround

Add onSelect="" on listboxes