Chihuahuas and great danes are not, practically speaking, interfertile. You can concoct devices using stepladders and so on, but a male chihuahua can't reach a female great Dane, no matter how receptive a posture she adopts, and I don't even like to think about a male great Dane and a female chihuahua. And even if you inseminate a female chihuahua with a male great Dane, I have grave doubts about the course of the last few weeks of gestation.
However, chihuahuas and pekingese are interfertile, as are pekingese and cocker spaniels, as are cocker spaniiels and standard poodles, as are standard poodles and labrador retrievers, as are labradors and great Danes.
My experience with animal breeding is limited to having a neighbor borrow my male siamese cat. (For his female cat, lest the mind wander.)
Initial results were extraordinarily loud and presumably painful for one or the other.
I'm sorry to say that although there were offspring from the mating, there are no living descendents.