You cannot utilise a single LUN > (2TB -512b) on ESXi 4.0.
First question would be why you're building such an old version? I'm aware the answer could well be related to support for your older hardware.
The general rule is "one disk/LUN = one partition = 1 vmfs datastore". If you want to break this storage up into two datastores that come in under the 2TB limit, you need to look at what your storage vendor offers around creating two smaller LUNs. I know with, for example, HP hardware, you can create one physical RAID array, with two "local disks" under it to achieve this effect.