I have a gold coil Colibri on my Aries 3 with the 10.5i arm and I think it is a magic combination. I have never heard a sibilance problem. The mids and highs are magic, and I have no complaints about the bass but do not listen to much really heavy bass music. However my RL mastered LZ II sounds great with very pronounced bass. Also VdH is making these with longer cantilevers these days.
However, obviously different systems will provide different presentations. Also, I have never heard a Zyz cart so cannot comment on how the Colibri will stack up against that.
However, obviously different systems will provide different presentations. Also, I have never heard a Zyz cart so cannot comment on how the Colibri will stack up against that.