No.
The problem in your case does not necessarily have to be IPv6 (which is unsupported and completly ignored by the Smart Lock), but could also be that the ZTE NAT solution does not allow/offer stable, low traffic tcp connections. In some scenarios we’ve seen tcp connections dropping as frequent as every 5 minutes, which leads to reconnect attempts of the Smart Lock. This overhead leads to a significantly increased power consumption of the Smart Lock.
With the current implementation the Smart Lock does also reconnect to WiFi in case of a tcp connection drop, which could lead to problems with the WiFi router if it’s done too often. It could have been the reason why you did not get a “stable wifi connection” too. There will be some changes to this logic with the next release, which is already in beta since some time.