Difference between Equanimity which is diversified and Equanimity which is unified
The Pali version of this expression identifies equanimity that is diversified as upekkhā nānattā nānattasitā and equanimity which is unified as upekkhā ekattā
ekattasitā.


  Evameva kho, gahapati, ariyasāvako iti paṭi­sañcik­khati:
  ‘rukkha­phalū­pamā kāmā vuttā bhagavatā bahudukkhā bahupāyāsā, ādīnavo
  ettha bhiyyo’ti. Evametaṃ yathābhūtaṃ sammappaññāya disvā yāyaṃ
  upekkhā nānattā nānattasitā taṃ abhinivajjetvā yāyaṃ upekkhā ekattā
  ekattasitā yattha sabbaso lokāmisūpādānā aparisesā nirujjhanti
  tamevūpekkhaṃ bhāveti
  Potaliyasutta [Pali]


Following excerpt from Excursions Into the Thought-World of the Pali Discourses by Bhikkhu Analayo explains them in detail.


  The unified equanimity of deeper Jhāna experience is considerably more
  refined than worldly types of equanimity that are based on diversity,
  upekkhā nānattā nānattasitā
  
  Excursions Into the Thought-World of the Pali Discourses
   By Bhikkhu Analayo


So in summary,
equanimity that is diversified = undeveloped mind
equanimity which is unified = a mind at Jhāna level