According to the Online Etymology Dictionary, the exclamation 'Zounds!' comes from the phrase 'God's wounds'. This seems to suggest that the original pronunciation rhymed with 'wounds' rather than 'hounds'. Does anyone know if that is the case?
At the time this imprecation was common wound was variously pronounced, with either /ɑu/ or /uː/,† so both pronunciations are attested. OED 1 reports these spellings: ‹zownes›, ‹zoones›, ‹'zons›, ‹zons›, ‹dzownds›, ‹sownds›, ‹zwounds›, ‹zauns›, ‹'zoons›, ‹zoons›, ‹'dzwounds›, and ‹zounds›
† Regular sound change would call for wound to end up the same as bound and found and sound, as indeed the participle did; but the rounded /w/ at the front interfered with this development. The language didn't settle on /wuːnd/ until the 18th century; in the 16th and 17th centuries both were available. Compare R&J, at the artificial boundary between 'II.i' and 'II.ii':
BEN: ’tis in vain
To seek him here that means not to be found.
ROM: He jests at scars that never felt a wound.
In theatrical productions the pronunciation "zoondz" is often used.