Solution :-
Revert back the oracle client to match the oracle database server version and restart. After that timezone will work as expected. however while investigating we did couple things -->
1. Changed the user timezone setting on MTA server
2. Changed the MTA server timezone
3. on Marketing Adobe Campaign side changed user timezone
4. on Marketing Adobe Campaign side downgrade the oracle client on app and web server to match the database version i.e. 12.1.0.2.0
5. Restarted all