<p>Forming-limit diagram, FLD, experiments and numeric simulations, using a crystal-plasticity visco-plastic self-consistent, VPSC, code, were conducted for a Zn20 alloy: in the rolling, RD; diagonal, DD; and transverse TD directions. The virgin material and the material after uniaxial and equi-biaxial prestrains were considered. Two techniques for determining the limit strains were used, a Bragard-type analysis and a statistical analysis, Merklein/Hotz, MH, that examines strains within the zone where the instability forms. A key to the successful simulation of the measured FLDs was the precise measurement of the texture of the initial material and texture after the prestrains. The zinc’s FLD was different than that of steel and aluminum when subject to prestraining. For zinc, the uniaxial and equi-biaxial prestrain FLDs were above that for the virgin material by an amount equal to the prestrain. This behavior was attributed to continuous dynamic recrystallization, XCRD. The simulations faithfully reproduced the Bragard-type experimental FLD measurements for all three orientations. However, when the FLD was calculated from strains within the instability zone, MH analysis, the material deviated from classic behavior for the RD and possible DD orientations. In these cases, fracture not instability likely dominated the failure process. For the TD orientation, the MH analysis consistently followed the Bragard-type FLD results. For this orientation, the developing instability was parallel to an existing anisotropic microstructure, which facilitated the instability’s formation.</p> Graphical Abstract <p></p>