Can you have two different lawyers work on different aspects of a tough divorce case---one for the financial/one for the custody issues: 2 diff. firms

Absolutely!  The better family law attorneys should be fine handling financials even when a business is part of the marital property.  In extreme cases when a larger corporation or several complex holdings are involved, it may be advisable to retain separate attorneys. The problem sometimes becomes getting good attorneys willing to co-counsel.  The better ones will be used to flying solo and would need to see a need themselves for assistance on the financials.