Standard best practice in Blackbaud NetCommunity is to only have one form part on a page at a time.  This is because the Javascript used for one form part (such as a donation form) can interfere with another form parts on the page.

Form parts include any part that requires input from the user.

Alternative Solution:
You can place a Formatted Text & Images part on the page  which includes a link to a separate page on which the other form part is enabled.