Inclusion Criteria:

          -  Male or female participants; age ≥ 18 years

          -  Pathologically confirmed nonsquamous NSCLC that is metastatic, locally advanced, or
             recurrent with progression

          -  Arm A participants must fulfill one of the following:

               -  Participant has a genetic alteration (mutation or rearrangement) and has received
                  all available targeted therapy. Previous treatment with chemotherapy or PD-1/-L1
                  therapy is not allowed.

               -  Participant has not received any therapy for the disease under study and standard
                  therapy is refused.

               -  Participant has progressed on PD-1/-L1 therapy (monotherapy or combination
                  regimen). Previous treatment with chemotherapy is not allowed.

               -  Participant has progressed on PD-1/-L1 therapy (monotherapy or combination
                  regimen) and has received less than 4 cycles of carboplatin/pemetrexed and
                  further chemotherapy is appropriate.

               -  Participant has received any number of prior treatments and is without
                  alternative or curative therapy.

          -  Arm B participants must fulfill one of the following:

               -  Participant has a genetic alteration (mutation or rearrangement) and has received
                  all available targeted therapy. Previous treatment with chemotherapy or PD-1/-L1
                  therapy is not allowed.

               -  Participant has not received any therapy for the disease under study and standard
                  therapy is refused.

               -  Participant has received any number of prior treatments and is without
                  alternative or curative therapy.

          -  Arm 1 and Arm 2 participants must have a sensitizing epidermal growth factor receptor
             (EGFR) mutation with disease progression or treatment intolerance after one or more
             approved TKIs. Previous treatment with chemotherapy or PD-1/L-1 therapy is not
             allowed.

          -  No TKI therapy within 5 days of Cycle 1 Day 1

          -  The last dose of previous investigational therapy is at least 4 weeks or 5 half-lives
             prior to Cycle 1 Day 1.

          -  Must have at least 1 measurable lesion per Response Evaluation Criteria in Solid
             Tumors (RECIST v1.1)

          -  Eastern Cooperative Oncology Group (ECOG) performance status score of 0 or 1.

          -  Confirm that an archival tissue sample is available and ≤ 24 months old; if not, a new
             biopsy of a tumor lesion should be obtained at screening

          -  Adequate organ and marrow function

        Exclusion Criteria:

          -  Use of any live vaccines against infectious diseases within 4 weeks (28 days) of
             initiation of investigational product

          -  Is pregnant or breastfeeding or expecting to conceive or father children within the
             projected duration of the study, starting with the pre-screening or screening visit
             through 30 days after the last dose of etrumadenant, 90 days after the last dose of
             zimberelimab or pembrolizumab, or 6 months after the last dose of pemetrexed,
             whichever is longer

          -  Any active autoimmune disease or a documented history of autoimmune disease or
             syndrome that required systemic treatment in the past 2 years (ie, with use of
             disease-modifying agents, corticosteroids, or immunosuppressive drugs), except for
             vitiligo or resolved childhood asthma/atopy

          -  Prior malignancy active within the previous 2 years except for locally curable cancers
             that have been apparently cured, such as basal or squamous cell skin cancer,
             superficial bladder cancer, or carcinoma in situ of the cervix, breast, or prostate
             cancer

          -  Prior use of an adenosine pathway targeting agent

        Due to potential for drug-drug interactions with etrumadenant, participants must not have
        had:

          -  Treatment with breast cancer resistance protein substrates or P-glycoprotein with a
             narrow therapeutic window, administered orally within 4 weeks or 5 half-lives of the
             drug (whichever is longer) prior to initiation of study treatment.

          -  Treatment with known strong cytochrome P450 3A4 (CYP3A4) inducers and strong CYP3A4
             inhibitors within 4 weeks or 5 half-lives of the drug (whichever is longer) prior to
             initiation of study treatment