Can a dog breed with a cat? How about a turtle with a tortoise?

No, they can't.
Cats and dogs are completely different species, so you can't really use that as an argument, or valid point.
DONT READ PAST THIS IF YOU ALREADY HAVE A BIASED NOTION IN YOUR MIND.
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Ignoring all forum/community morals as the OP has suggested.
Cross breeding relies heavily on chromosome similarities (and a bunch of other factors.) So trying to breed a cat and a dog wouldn't work because they are completely different species and have completely different chromosomes that aren't compatible.
A horse and a mule on the other hand have very compatible characteristics, and thusly are able to cross breed to create a hybrid, in this case, a donkey. It is considered successful crossbreeding because the donkey gains positive attributes from BOTH parents. For those reasons it's morally accepted and been a popular practice throughout the world.
Now, a panther and a veiled. if you actually put a male and female of each together I not too certain how that would turn out or if it would be a good safe idea either (for the sake of both chams)
BUT
If you were to somehow get a professional to artificially inseminate a female panther with veiled semen, my hypotheses is that you WOULD be able to hatch something out of that egg(I haven't looked into chromosome compatibility or anything scientific, this is just a semi-educated far-fetched guess). Now you have to wonder...is the hybrid coming out of that egg safe? will it have full function of all its organs? ect. You may yield different results if you insenmenated a female vield with panther semen.
To come to a conclusion, it would take years of observations (if you managed to hatch something) and you would have to repeat the experiment several times to get conclusive results, constantly recording cause of death, life span, living conditions ect.
So bottom line.
Can it be done? ---- High possibility (my opinion)
Is it practical? ---- No. (too much time, too expensive, unfair to any offspring born defective)
Should you do it? No (again I'm not assuming you are, just my opinion)