Has anybody used a Canon EOS External Flash (300EZ) with an Olympus C750?
The handbook (see below) is fairly adamant that it shouldn't be tried but I
guess they would like you to buy the Olympus model!

(7) If a flash unit or other accessory TTL flash that has additional
communications functions other than the FL-20 or FL-40 is used, it may not
only fail to function normally, but may also cause damage to the camera