I have a win2k8 which I need to delete forward lookup zone of several domain computers, will the domain recreate the forward lookup zone and the associated reverse Lookup Zone? if so, how long will it take to propegate to DNS?
The question isn't clear but I think you are inquiring of dynamic DNS behaviour. Zones arent created by default by DDNS record registrations. But subdomains can appear within an existing zone if a machine tries to register a record that falls within a forward or reverse lookup zone thats already exsting.
I think you are talking of AD integrated zones here from "propagation" perspective. If yes, AD replication will decide propagation times. You have site links replication intervals and the convergence topology to consider. Without the replication topology its hard to say. Is it a simple hub with multiple spokes hanging off it? Or tiered topology with intermediate hubs? Once the changes themselves are replicated, DNS also wont know until it polls AD for any changes which can take a further 3 mins or so. See dspollinginterval reg key as configurable at http://technet.microsoft.com/en-us/library/cc756116(WS.10).aspx.
Also note that clients that have resolved the deleted records will cache the response for a period based on TTL of record and may not attempt to resolve until the cached response expires.