Combining different elements of Dragon Slayer Magic is one thing. Natsu did it, Gajeel did it, and Future Rogue pulls it off. When Natsu eats the God Slayer Magic, he has it briefly, then loses it. I would assume the same thing if he tried to eat fire element Demon Slayer Magic, which is get it briefly, then lose it. But to get another element of magic from an entirely different field of slayer magic? I'm gonna say...no. Same field of magic but a different element, sure, same element but different field, for a little while, different element and different field, no.
Dragon Slayer-Lightning Yes
God Slayer-Flames Temporary
Demon Slayer-Ice Not without serious writer's plot armor