300.3(C)(3) prohibits conductors from different services or different circuits derived from different services in the same raceways or enclosures, except as permitted in 300.5(D).300.5(D) permits conductors of different services or circuits derived from different services in the same enclosures where:- The enclosure is part of a separately metered service- The conductors are separated by a permanent barrier- The conductors are not terminated or spliced within the enclosureIn your situation, the different sets of conductors are likely from different services, so they cannot occupy the same enclosure unless they meet the requirements of 300.5(D).To provide a low impedance path via EGC and neutral bonding for both sets of conductors without paralleling the neutrals from different transformers, you could use a common bonding jumper to connect the EGCs and neutral conductors of both sets of conductors outside of the enclosure. Flag for review