Unfortunately, you cannot, as the combined accounts must be of the same type.
A single RMD withdrawal can be made
to cover the entire required amount for the year. However, the combined accounts must be of the
same type. For example, two traditional
IRAs can be combined, not an IRA account and a pension account.
If the accounts are combined, a taxpayer may
take a withdrawal from any chosen account in the amount of the total required
minimum distribution required for all accounts.
https://www.irs.gov/Retirement-Plans/RMD-Comparison-Chart-IRAs-vs.-Defined-Contribution-Plans
