Zlatan and Lukaku can be a good partnership in 3-5-2 or the diamond. The diamond actually looks really interesting for me :
De Gea
Valencia - Bailly - Jones - Young
Matic
Herrera/Fellaini - Pogba
Mikhi
Zlatan - Lukaku
Its only is the flanks will be quite exposed on defending but can be used against parked buses. Not to mention we'll have both Rashford and Martial on the bench also!
The 3-5-2 also :
De Gea
Bailly - Lindelof - Jones
Valencia - Matic - Pogba - Young
Mikhi
Zlatan - Lukaku
I can see this happening more than the diamond, may be in some away games in Europe. The flanks are well covered by the wing back and defender behind him, while Zlatan will drop deep to help Mikhi and Pogba in building the attack, interesting. Again Rashford and Martial are still on the bench, though.
One thing for sure : Zlatan will give us numerous options either as a starter in some games or a sub in others.