Designing many to many relationship between three entities

Designing many to many relationship between three entities

I'm having trouble modelling this situation. I'm designing a
location-based coupon system. A user can define zones and offers and then
associate each offer to multiple zones. Also each zone can have more than
one offer. So zone and offer have a many to many relationship. The user
entity owns both entities. A zone and an offer can only be associated if
the same user owns both of them. A diagram can be very helpful. Thanks.