Unfortunately, Sunni and Shiites appear to only find commonalities rather than differences, when they are both radical, and have a common enemy – Israel.
One of Hamas’s leaders, Mahmoud Al-Zahar spent one week recently in Beirut. The Hamas leader Ismail Haniya is also expected to visit Beirut soon. Despite the fact that Hamas is essentially a Sunni radical terrorist organization and Hezbollah is a Shiite one, they nonetheless find mutual interests in fighting Israel.
Hamas’s leaders visits to Beirut reported here.