Funding the next major Zcash entity is not in the exact wording of ZIP-1014, but it was included in the early dev-fund discussions (ZIP 1001 through 1013), especially in ZIP-1006, and ZIP-1012 that states:
" Priority will be given to Major Grants that bolster new teams with substantial (current or prospective) continual existence, and set them up for long-term success, subject to the usual grant award considerations (impact, ability, risks, team, cost-effectiveness, etc.). Priority will be given Major Grants that support ecosystem growth by mentorship, coaching, technical resources, creating entrepreneurial opportunities, etc." source: ZIP-1012 discussion
I think no amendment is required. Based on the wording of ZIP-1014, there is no prohibition on ZCG funding a community effort to establish a third entity. Today, a community member can create a grant proposal to fund a third entity, and the grants committee can approve those.
I believe this was also why members of the community, who wants the establishment of a 3rd entity during the dev-fund talks, did not push too hard on creating the 3rd entity since ZIP 1014 allows for funding of next major Zcash entities. This is also why ZCG grant slice is bigger than ECC or ZF.