"It's sausage to me." is rather tame, would fit "I don't care" or "I couldn't care less.". The blood pudding is the same, but feels a bit archaic/backwardly.
There's also: "This goes straight past my arse." - which might be a better match for "zero fucks" in terms of tone and vulgarity. But even that feels more like "I don't give a shit" rather then "Zero fucks given". I don't think there's a perfect German translation of "Zero fucks given" that captures all the nuances.
"The dog shits on it." (mentioned for another language) exists in German as well. Feels a bit more aggressive/confrontational than "It's sausage to me." (It's also more of a "nobody cares" rather than an "I don't care")