Can F5 LTM be used to connect two DMZs (at separate locations) ?

For as long as you have the network connectivity from BigIP to the Pool Member, I see no reason why not. The Pool Member you specify can be anywhere in the world. In such a case, I would still try to avoid 50/50 load balancing for the latency reasons. If possible, go with a solution where you always route to the closest DMZ, and only after the number of connections hits a certain count, you start balancing to the DMZ which is further away.

Thank you Hannes.