How do I play WotLK with MoP?

How do I play WotLK 3.3.5a with MoP 5.4.2?

You can't do something like this. You need to download 3.3.5a client and place to another directory. Only this way you can play LK and MoP

you cannot play any old expansions trough a new client. Wotlk client 3.3.5a only works for Wotlk 3.3.5a and same for MoP client 5.4.0