I researched this as had horse clippers but needed sheep one and the conclusion was 'no'. You can get sheep combs for some horse clippers but motor wise they are really not up to the job for any length of time. So you could risk it doing a couple of sheep slowly but I wouldnt try for a flock. I ended up buying second hand lister sheep clippers and kept the Heiniger progress ones for the horses. Also ,the horse clippers I have are mains electric 24V which is fine as we have electric in the stables but we shear the sheep in a pen in the field so I needed ones which could run from a car battery 12V.
If you do get specific sheep shears they do hold their value very well.