I personally have no faith on Immigration solicitors in Ireland. They are absolute waste of time and money grabbers. Once you pay them, this is the last time you will see them.
However, if you are still interested to hire a solicitor you can contact Brophy solicitors Or Sinnott solicitors. (Google them and you will find their offices).
Zambrano application is a straight forward process and you can get most of your help on the forum here or on the DOJ website.
All correspondence in relation to the Zambrano Judgment should be sent to below address through registered post:
Repatriation Division,
INIS,
13-14 Burgh Quay,
Dublin 2
You can get further help from the below DOJ links:
http://www.inis.gov.ie/en/INIS/Pages/WP11000037
http://www.inis.gov.ie/en/INIS/Pages/WP11000038
If you have any question, please post here, the members are very helpful...and Good Luck