Multinodular Goiter: This is the most likely diagnosis given the presence of multiple nodules in both lobes of the thyroid gland, along with inhomogeneous parenchyma. The variation in nodule size and composition (heterogeneous and complex with solid and cystic components) is consistent with a multinodular goiter, which is a common condition characterized by the enlargement of the thyroid gland due to the growth of multiple nodules.

Thyroid Adenomas: The presence of heterogeneous nodules with minimal color flow along the periphery could suggest thyroid adenomas, which are benign tumors of the thyroid gland. These are common and can be multiple, contributing to a multinodular appearance.
Thyroiditis (Chronic): The inhomogeneous parenchyma and the presence of nodules could also be indicative of chronic thyroiditis, an inflammatory condition of the thyroid gland that can lead to glandular destruction and nodular formation.
Papillary Thyroid Carcinoma: Although less likely given the absence of specific malignant features, papillary thyroid carcinoma can present as multiple nodules within the thyroid gland. The complex nodule with solid and cystic components in the left lobe warrants further investigation to rule out malignancy.

Medullary Thyroid Carcinoma: This rare malignancy can present with multiple nodules and is important to consider due to its potential for aggressive behavior and the need for early intervention. Family history and genetic testing may be relevant.
Anaplastic Thyroid Carcinoma: Although very rare and typically presenting with a rapidly enlarging neck mass, anaplastic thyroid carcinoma is a highly aggressive malignancy that could be considered in the differential diagnosis of a multinodular thyroid gland, especially if there are symptoms of compression or invasion.
Metastatic Disease to the Thyroid: Rarely, metastases from other cancers can involve the thyroid gland, presenting as multiple nodules. This would be more likely in patients with a known history of cancer.

Thyroid Lymphoma: A rare malignancy that can involve the thyroid gland, often presenting with rapid enlargement and potentially multiple nodules. It is more common in patients with a history of Hashimoto thyroiditis.
Parathyroid Adenomas or Hyperplasia: Although not directly related to the thyroid nodules, parathyroid pathology can sometimes be considered in the differential diagnosis of neck masses or nodules, especially if there are abnormalities in calcium levels.