Quite interesting what you've said, thanks for your opinions so far

K9 Soul - (no offence intended just in case you take this the wrong way) I do think that you have confused cross-breed with hybrid. The only reason I say this is because of the use of the word 'breed' in the term cross breed. To me, that indicates that the cross is between two animals of the same species, just different breeds of the same species.

Hybrid I'm fairly certain I've heard used for years as a term for a cross of two different species, as you have described (Liger, Zonkey etc).
I've just done a search on Wikipedia and they use the term Zeedonk for a Zebra/Donkey cross!