• Must sign the informed consent form (ICF) and be capable of giving written informed consent, which includes compliance with the requirements and restrictions listed in the ICF

• Confirmed diagnosis of a R/R B-cell malignancy

• Protocol-defined measurable disease

• Stable Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 to 2

• Adequate organ function

• Female participants of childbearing potential must be willing to use a highly effective method of birth control and refrain from egg donation for the duration of the study and for 30 days after the last dose of BGB-16673 or zanubrutinib, 60 days after the last dose of glofitamab, or 90 days after the last dose of sonrotoclax or mosunetuzumab. A negative urine or serum pregnancy test result must be provided 10-14 days before the first dose of study treatment

• Nonsterile male participants must be willing to use a highly effective method of birth control and refrain from sperm donation for the duration of the study and for 30 days after the last dose of BGB-16673 or zanubrutinib, 60 days after the last dose of glofitamab, or 90 days after the last dose of sonrotoclax or mosunetuzumab

• Substudies 1, 3, and 4 Inclusion Criterion:

‣ Adequate renal function as indicated by estimated glomerular filtration rate (eGFR) of ≥ 50 mL/min

• Substudy 2 Inclusion Criteria:

‣ Bruton tyrosine kinase (BTK) inhibitor-naive, or previously received treatment with a covalent BTK inhibitor and discontinued for reasons other than clinical progression

⁃ Adequate renal function as indicated by eGFR of ≥ 30 mL/min