The standard for discovery is whether the sought documents are reasonably likely to lead to discoverable information. If your financials are somehow relevant to the case yes they are discoverable.
Previous response is correct. If the requested information in relevant to the subject matter of the action or reasonably calculated to lead to the discovery of admissable evidence, the propunding party may ask for these documents. For example, if an injured plaintiff claims he suffered loss of income, the defendant may certainly aske for evidence supporting the loss such as W-2s. Sometimes parties object to producing tax returns not so much on privilege grounds but on the ground that the request invades the responding party's right of privacy under the state's constitution and federal constitution. However, if the tax returns are otherwise relevant, the privilege argument may be a losing argument. You may be able to work out an agreement to black out certain information in the tax returns or otherwise limit the scope of the production.
This response is for information purpose only and does not constitute a legal advice. This response does not create an attorney-client relationship.
You've got employment claims against your employer and are presumably claiming lost income, so these documents would probably meet the fairly low standard for discovery in the cases. It might be psosible to seek a protective order for sensitive documents, depending on the claims and uses involved.
I strongly suggest hiring a lawyer. itigating 3 cases simultaneously is like performing 3 different kinds of surgery on yourself and pro per litigants usually do poorly against lawyers when they try.
PLEASE READ THIS BEFORE YOU COMMENT, EMAIL ME OR PHONE ME. I'm only licensed in CA. This answer doesn't make me your lawyer, and neither do follow-up comments and/or emails and/or phone calls, and you shouldn't expect me to respond to your further questions if you haven't hired me. We need an actual agreement confirmed in writing before any attorney-client relationship is formed. This answer doesn't constitute legal advice, and shouldn't be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue.