Deutsche-Commerzbank merger approval said to rest on implementation
European regulators are concerned by Deutsche's lack of "ruthless brutality"

Regulators are said to be concerned about whether a failed integration would leave Deutsche in a position with an even bigger problem to sort out.
On paper, mergers and deals like this are always great for the industry as a whole; but the process is nothing but a pain for both regulators and staff of the respective banks. Tying up of systems and internal processes and trying to synchronise all the back-end data is never a fun thing for anybody involved.
But at least continued talks will help to boost banking stocks in the region as seen yesterday; and that should continue to today as well.