Purpose: This retrospective study aimed to compare extended sinus lift and extramaxilla surgical protocols for restoring severely atrophic maxillae with zygomatic implants (ZIs) and evaluate their clinical effectiveness. Materials and Methods: The study includes patients who were treated at a dental clinic in Italy from 2012 to 2022. These patients received fixed screw-retained complete dentures supported by either two or four zygomatic implants (ZIs). The patients underwent a minimum one-year follow-up post-loading, following two protocols: the hybrid and the quad protocol. Digital planning incorporated CBCT scans, intraoral scans, and digital prosthetic plans within implant planning software. Surgical techniques involved extended sinus lift and extramaxilla techniques methods, utilizing the ZAGA approach for ZI placement. Results: The results showed that out of 19 patients with a mean age of 65.3, a total of 56 zygomatic implants (ZIs) and 20 standard implants were used, with no failures observed in either the implants or the definitive prostheses, resulting in a 100% survival rate. According to the ORIS criteria, overall success was achieved in terms of implant stability, sinus health, peri-implant soft tissue condition, and prosthetic function. Only two ZIs (3.6%) exhibited minor gingival recession and moderate thread exposure, which were closely monitored through professional hygiene maintenance. Conclusion: Both the extended sinus lift and extramaxilla protocols demonstrated comparable clinical outcomes and minimal complications in the restoration of severely atrophic maxillae with Zygomatic Implants (ZIs). However, further extensive studies involving larger, multicenter designs and longer follow-up periods are needed to validate and refine these outcomes.