@doudoune23 Yes this is supported (as is vSphere Replication from any 'faster' to any relatively 'slower' datastore).
However, the number of hosts and VMs involved in the replication may be a limitation as the overhead from this may be easily handled on the All-Flash cluster but over-burden the Hybrid cluster:
https://docs.vmware.com/en/vSphere-Replication/8.3/com.vmware.vsphere.replication-admin.doc/GUID-1FF...
Just a point though, your question is bit too broad: One cluster doesn't equal another - an 8-node Hybrid cluster may be able to pump more IO than a 4-node All-Flash cluster, furthermore a very well specced 4-node Hybrid cluster might out-perform a relatively slow 4-node All-Flash cluster (see all SATA devices, Read-intensive devices, low Cache:Capacity ratio, dedupe+compression enabled, RAID5 SP), my main point here being that Hybrid =! slower or less performant than All-Flash (other than perhaps raw latency figures).
