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To a blind horse, nodding and winking mean the same thing.
Literal
Blind-horse [for-には] nod [even-ても] eye-gesture do-[even-ても] same thing.
A proverb built on a double concessive — ~ても…~ても ('whether X or Y'). The claim is that some visual signals (a nod, a wink) are lost on someone who can't see them, so they amount to the same thing: nothing. 目配せ ('winking, eye-signalling') is a compound of 目 ('eye') + 配せ (from 配る 'distribute'). 盲馬 literally 'blind horse' — now considered sensitive language, but common in older proverbs.