Difficulty is the avg # of diff 1 shares per BLOCK. As indicated above shares are usually diff 1 (unless otherwise specified).
So current BLOCK difficulty is 1733207.5138484
It will take on average 1733207.5138484 shares (diff 1) to solve a block.
It will take on average 1733207.5138484 * 2^32 = 7.4E+15 hashes to solve a block (7.4 quadrillion hashes).
Shares are arbitrarily difficulty 1 but they don't need to be. p2pool for example has a share diff of ~680.
Thus it takes on average 1733207.5138484 / 680 = ~258 p2pool shares (of difficulty 680) to solve a block.
It takes on average 680 * 2^32 = ~3 trillion hashes to find a p2pool shares.
The number of hashes to find a block is still the same. 2^32 * 680 * 258 ~= 7.4 quadrillion hashes.