You can pull off multiple DMs in the same world, but even with only 2 DMs and a great deal of coordinating there are problems. I have been DMing with another DM for years that way. I have also seen multiple DMs for the same party both in Earthdawn and in Shadowrun, and it did not work out well.
Best solution? Start your own campaign with you as the single DM.
Second best solution? Have one "Head DM" who can veto any and all decision from the co-DMs, and who determines what is appropriate for the campaign. The co-DMs would run more sporadic adventures, and run all problematic items by him (and the players would have to accept that anything deemed to powerful would be adjusted by the Head DM).
Third best solution? Talk with the other DMs, make strict guidelines for treasure, advancement etc.
Fourth best solution? Stop DMing, and tell the others that the power level of the party makes it impossible for you to prepare an adventure.
(I know many say "just challenge them accordingly", but I personally are not willing to enter an arms race with PCs (and other DMs), nor to spend a lot more time preparing an adventure just compensating for uber-items. I have better uses for my time than that.)