Longbows are about a thousand or two years off the time period for the Greeks to worry about... but assuming that you mean progress wise for English in the future of this theoretical mecha containing past we are discusing...
Longbows can easily shoot through the 3/8ths of and inch to whateverever amount less than an inch platemail got up to... Walker mecha would have armor that its several inches thick and probably muliple layers... so you'd have to have an absurd draw strength on the bow to get through the armor... like cybernetics level strength here.
Longbows can easily shoot through the 3/8ths of and inch to whateverever amount less than an inch platemail got up to... Walker mecha would have armor that its several inches thick and probably muliple layers... so you'd have to have an absurd draw strength on the bow to get through the armor... like cybernetics level strength here.