Pyrochlore oxides (A2B2O7) – and other fluorite-derived complex oxides – are interesting for not only their wide variety of desirable properties, such as ionic conduction and radiation tolerance, but also for their complex defect formation and disordering mechanisms that often give rise to their properties. We have used neutron total scattering to study in detail all structural aspects of the disordering of pyrochlore which involves randomization of both cation and anion sublattices. By means of diffraction and pair distribution function analysis of a Ho2Ti2-xZrxO7 (x = 0.0-2.0) solid solution series, the disordering mechanism was studied simultaneously over multiple material length scales with novel insight into the local atomic arrangements. With increasing Zr-content, the series exhibits an order-disorder transformation from pyrochlore (space group: Fd-3m) to defective fluorite (space group: Fm-3m) across a narrow compositional range (x = 1.0-1.5) over the long length-scale, while the local atomic arrangement changes gradually to a weberite-type structure (space group: C2221) over the whole compositional range. This distinct disordering scheme can be explained by the movement of a 48f oxygen to a vacant 8a site, creating 7-coordinated Zr4+ sites that produce local weberite-type building blocks. These building blocks accumulate until a critical Zr-content (x ~ 1.2) is reached which triggers the rearrangement of weberite-type units into long-range structural defective fluorite.