188.8.131.52.in-addr.arpa canonical name = 34.0-24.
Change the CNAME target from (34.0-24.) to just (34.0-24) with no period. This nslookup result should be '34.0-184.108.40.206.in-addr.arpa' if you configured everything properly. And you would need a '0-220.127.116.11.in-addr.arpa' zone in this case too.
First off, I do not think you need to seperate your zones out like you have been. The only reason I feel you need a 0-24, or whatever, sub-zone is if you are trying to assign differnent subnets of the zone to different clients, so each client can only access and change their subnet. If you are just using the zone for yourself and don't have other users/clients trying to access differnet subnets then just create the main zone as follows:
Create a zone 100.92.188.in-addr.arpa.
Add records in this zone:
NS [empty] ns1.itgreen.it
NS [empty] ns2.itgreen.it
PTR 34 webhosting01.example.com