Very few slaves sold across the Atlantic were sold to Europeans by Muslims. The Muslims were well inland, barred from the coast by rich, powerful pagan slave-trading kingdoms.
Probably a good many of the slaves these kingdoms sold to whites were originally enslaved by Muslims and sold to the pagan kings by them. But there was little direct contact between Europeans and Muslims in the slave trade.
Plus the fact that moslems would castrate the males they captured, cutting EVERYTHING off. That is why blacks never reproduced in Arabia.
The emasculated males then would be put to digging wells and other sort of killer jobs. If one died, another was cheap just across the mountains. There was an endless supply.