VMware Esxi and VCenter management

Hello All,

i have a cenario , with two stand alone host and a VCenter

1. ESXi 4.1.0( stand alone host -cisco hardware) with  vSphere 4 Foundation License

2. ESXi 4.1.0 ( Stand alone host - cisco hardware ) with  vSphere 4 Foundation License

and a VCenter 5.1 with some Cluster and Datacenter  with Dell hardwares( this has Vsphere 5 enterprise plus license )

is it possible to ceate a new cluster and add these two stand alone host in aVCenter to manage them all.

will the license be a conflict ?

will the hardware be a conflict ?

is there any know errors or problems that i would face ?

please suggest and provide your views on this

Thanks all in advance