Detection of builtin chains depends on only them having uppercase names, but firewalld doesn't honor this assumption when it creates its internal chains. It has chains like FORWARD_IN_ZONES.

The regular expression for rules will capture everything past the chain name into the group "conditions". That is because capturing the "target" group is conditional where it should be mandatory. I added a patch that fixes this and which also adds support for counters (if iptables-save was run with "-c" option).
patch.txt

how to install it? thanks.