Yes, a ZBIT2 would allow you to feed both balanced outputs into it and then feed the single-ended output into the ZROCK3.
I was going to do that but then discovered a killer deal on a Goldpoint 2 XLR input to one XLR output switcher with a stepped attenuator--about one third the list price, and as I already had an extra XLR cable that was a great boon for me, and works excellently for my two sources (PS Audio DSD DAC Mk2, PS Audio NuWave Phono Converter with balanced output).
https://www.goldpt.com/sa2x.htmlAs for XLR cables. . . I really haven't found "buget" ones that work for me. I am using VooDoo Cable Stradivarius Amati which i was lucky to get at a discount--they are very expensive--last decade. In another system I am using these, which are quite good, and discounted here:
https://partsconnexion.com/xlo-signature-3-interconnect-cable-1m-xlr-1/