No. The private key only allows you to derive the master private key for that specific Zpub in question, it does not compromise the other Zpubs. However, since the attacker has one of your Zpriv (master private key), the attacker can use that master private key to sign for transactions, assuming another person is willing to sign it too. A single compromised Zpub and private key doesn't affect the other signers.

Because the combination of a Zpub plus any one individual private key is enough to derive the Zprv and all the associated individual private keys.

I'd like to understand this completely in reference to a multisig setup.  Let's use a 2 of 3 multisig as an example.  If someone were to have all 3 of the Zpubs and then you accidentally leaked one of your private keys.  Is it possible to derive the 2nd private key?  And if so then the attacker can sign a transaction from this wallet.

Leaking a single private key would only allow an attacker to use that private key and the corresponding master public key to derive a single master private key. In the case of a multi-sig wallet, funds would still be safe since the attacker would only have one master private key, and not the threshold number of master private keys. For the coins to be at risk, OP would have to leak multiple private keys derived from different master private keys, which is very unlikely if his multi-sig wallets are all stored separately (as they should be) and he takes reasonable security precautions.

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Throughout this thread, people are using Zpub and zpub interchangeably. They are not the same thing. zpubs are for P2WPKH addresses, Zpubs are for P2WSH addresses. See here for more info: https://github.com/satoshilabs/slips/blob/master/slip-0132.md

Probably not the best idea even if your need more than one of them to spend.

If your going to the trouble of using Multi-Sig then why keep the keys online?

Seems pretty stupid.

There are obvious reasons why people choose to transact with BTC. Two of them are privacy and the no intermediary that would potentially hold your funds.

Are you talking about the tax man or authorities with "the man"? I don't know everyone's stand on taxation and regulation but there could be some people trying to evade taxes or avoid getting flagged by using bitcoin.