I would to like access my clients to the 3 virtual machines depending on the client.
If by "depending on the client" you mean that you can identify your client by specific IP ranges/addresses, then it isn't that much of a problem. You can create Port Forwards with specific source addresses coming to the WAN IP to specific internal hosts. So for example:
Src | Dst | NAT
1.2.3.4/24 | <wan ip="">| 10.0.0.11 (Host 1 in DMZ)
2.3.4.5/32 | <wan ip="">| 10.0.0.12 (Host 2 in DMZ)
3.4.5.6/28 | <wan ip="">| 10.0.0.13 (Host 3 in DMZ)
That is completely possible. Only if you want to allow access from ANY (whole internet) or you want to address the same host twice with a source already configured (e.g. 1.2.3.4/24 shall also access 10.0.0.12) that would only be possible with proxies of any kind.
Otherwise just use different Forwardings for different clients :)</wan></wan></wan>