Inclusion Criteria:  Provision of signed informed consent (obtained according to institutional guidelines) prior to initiation of any study-related procedures. Age ≥18 years at the time of informed consent. Locally advanced or metastatic malignancy with one or more relevant biomarkers related to deoxyribonucleic acid (DNA) damage pathways Subjects must have received prior standard therapy appropriate for their tumor type and stage of disease, or in the opinion of the Investigator, would be unlikely to tolerate or derive clinically meaningful benefit from appropriate standard of care therapy, or no standard therapy exists for their tumor type/stage. Prior treatment with immune checkpoint inhibitors is allowed. Subjects must have at least one measurable lesion as defined by RECIST Guideline Version 1.1. Performance Status: Eastern Cooperative Oncology Group (ECOG) score of ≤2. Adequate hematologic and organ function Willingness and ability to release archival tissue Females of childbearing potential and male subjects must agree to use an effective method of contraception prior to the first dose and for 90 days after the last dose of ZN-c3. Willingness and ability to comply with scheduled visits, treatment plan, laboratory tests, and other study procedures.  Exclusion Criteria:  1. Any of the following treatment interventions within the specified time frame prior to C1D1:  Major surgery within 28 days (any surgical incision should be fully healed prior to study drug administration); Any chemotherapy within 14 days or 5 half-lives (whichever is shorter); Radiation therapy within 21 days; however, if the radiation portal covered ≤5% of the bone marrow, the subject is eligible irrespective of the end date of radiotherapy. Autologous or allogeneic stem cell transplant within 3 months. Current use of any other investigational drug therapy <28 days or 5 half-lives (whichever is shorter). Inability to discontinue treatment prescription or non-prescription drugs, or to discontinue consumption of food and herbal supplements, that are strong/moderate CYP3A4 inhibitors, P-gp inhibitors, or strong CYP3A4 inducers at least 14 days prior to start of study drug treatment Prior therapy with ZN-c3 or any other WEE1 inhibitor. A serious illness or medical condition(s) Unresolved toxicity of Grade >1 attributed to any prior therapies (excluding Grade ≤2 neuropathy, alopecia or skin pigmentation). Pregnant or lactating females (including the cessation of lactation) or females of childbearing potential who have a positive serum pregnancy test within 14 days prior to C1D1. Subjects with active (uncontrolled, metastatic) second malignancies or requiring therapy. Individuals who are judged by the Investigator to be unsuitable as study subjects. 12-lead ECG demonstrating a corrected QT interval using Fridericia's formula (QTcF) of >480 ms, except for subjects with atrioventricular pacemakers or other conditions (e.g., right bundle branch block) that render the QT measurement invalid. History or current evidence of congenital or family history of long QT syndrome or Torsade de Pointes (TdP). Taking medications with a known risk of TdP. Concomitant medication that leads to significant QT prolongation. Administration of strong or moderate CYP3A4 inhibitors or inducers and P-gp inhibitors