Inclusion Criteria:  NHL, relapsed from or refractory to at least 2 prior lines of systemic therapy (excluding radiotherapy and surgery); subjects must have failed or not be candidates for available standard therapy expected to provide clinical benefit. Female subjects of childbearing potential must have a negative serum pregnancy test and agree to use contraception while on study. Eastern Cooperative Oncology Group performance status ≤ 1.  Adequate blood and other organ function, defined by the following criteria:  Neutrophil count (ANC) ≥ 1.0 × 109/L. Platelet count ≥ 75 × 109/L at least 3 days after platelet transfusion (≥ 50 × 109/L permitted if the bone marrow is > 50% lymphoma cells). Hemoglobin ≥ 8.0 g/dL. Coagulation parameters ≤ 1.5 × upper limit of normal (ULN). Liver enzymes ≤ 3 × ULN and total bilirubin ≤ 1.5 × ULN. Creatinine clearance ≥ 60 mL/min.  Exclusion Criteria:  Received any of the following prior to start of ZN-d5 treatment:  Systemic administration of antineoplastic agents (including investigational agents) within the shorter of 28 days or 5 half-lives. Major surgery within 28 days. Radiotherapy within 14 days. Autologous or allogeneic stem cell transplantation within 60 days, or receiving immunosuppression for active graft-versus-host disease. Use of strong CYP3A4 inhibitors, P-gp inhibitors or QT prolonging agents within 5 half-lives, or potent or moderate CYP3A4 inducers within 14 days. Ongoing and clinically significant non-hematologic toxicity related to prior antineoplastic therapy. Presence of major cardiovascular system diseases (including QTcF > 480 msec). Positive serology for human immunodeficiency virus, hepatitis B, or hepatitis C unless no detectable hepatitis B or C viral load. Unable to take oral drugs or presence of severe gastrointestinal abnormalities. Active and uncontrolled clinically significant infection. Other active systemic malignancy or other severe, unstable, or poorly controlled acute or chronic medical conditions. Prior treatment with venetoclax or other BCL-2 inhibitors. Primary or secondary CNS lymphoma. Presence of post-transplant lymphoproliferative disease, Burkitt's lymphoma, Burkitt-like lymphoma, T lymphoblastic lymphoma and T lymphoblastic acute leukemia.