So I spoke with Product development guys. You can't run three freqs when the unit support two. In regards to using the B265LH, the best way is direct to the TZT3. The DI box is not needed. The B265LH is already supported and we sell versions with the 12 pin cable already connected. In your case using one from the UHD, you would need a 12 pin pigtail cable to wire it up. (pn TZ3-12P-PGT) If you have another complete 2/3kw transducer you want to run in addition, you would need a DI box to run that. If you have two TZT3 displays, one could run the B2265LH direct and the other could connect to the DI box on the other display. If you only have one TZT3, then it would be best to keep your UHD box as is and then run a DI box for the 2/3kw transducer.