That may be a good idea considering that when either company computes your withholding tax, they don't know about the income you have from other sources and higher income typically means a higher tax bracket (%).  Claiming 0 allowances results in a higher amount of tax withheld from your paycheck, meaning lower take-home pay, which could offset some or all of this differential between your true tack bracket (the one that includes all of your income) vs the tax bracket used to calculate your withholding at each company based solely on your income from that company.

You may end up needing to pay more than that.  I generally find it best to use the irs withholding calculator.  They generally make it available about February of the current year.  If you do it with your most recent paystubs, it can calculate what you will owe in taxes, how much will be withheld and tell you what to set your w4 for both jobs.

https://apps.irs.gov/app/withholdingcalculator/index.jsp