  We present postprocess AGB nucleosynthesis models with different
$^{13}$C-pocket internal structures to better explain zirconium isotope
measurements in mainstream presolar SiC grains by Nicolussi et al. (1997) and
Barzyk et al. (2007). We show that higher-than-solar $^{92}$Zr/$^{94}$Zr ratios
can be predicted by adopting a $^{13}$C-pocket with a flat $^{13}$C profile,
instead of the previous decreasing-with-depth $^{13}$C profile. The improved
agreement between grain data for zirconium isotopes and AGB models provides
additional support for a recent proposal of a flat $^{13}$C profile based on
barium isotopes in mainstream SiC grains by Liu et al. (2014).
