When I share those hadiths with sunnis they of course say Muhammad did not write things down himself, he had scribes do it.
The hadith do not say that, but I have read that interpretation. Try another take...
You can ask them was prophet Muhammad a good trader/merchant? They will say yes. You then tell them that the number system used at the time of the prophet was the
Abjad method (in which letters of the Arabic alphabet represented numbers) and this is what traders used at the time and for all mathematics. Did Muhammad use this system? If he did this means he could recognise letters. If he did not then he spent his entire trading career doing things by memory and every trader he dealt with was happy not to use the widespread Abjad method or he had someone with him all the time who recorded these trades/contracts for him but if so this has never been documented anywhere.
Did he ever disobey God? If they say no, then ask what did he do when he was revealed the very first revelation (according to them) i.e. 96:1
Read (imperative/command form, iqra) in the name of your Lord who has created.They will almost certainly say according to hadith the prophet replied he cannot read. So God commanded him to read and he replied he couldn't and never learnt to read for the rest of his life despite this command. If God commands X and I cannot do X at the time is it ok never to do X? Is prophet Muhammad a good example for believers to follow........ except with regards to learning to read... or...?
(please also see video and Edp's argument above) They are unlikely to concede anything but nice to see their reaction.