} else if (left != NULL && right == NULL) {
        Tree_Replace (node, left);
        Tree_DeleteBalance (t, node, 0);
        toDelete = left;
    } else { // if (left != NULL && right != NULL)
        Node successor = right;
        if (successor->left == NULL) {
            Node parent = node->parent;
            successor->parent = parent;
            successor->left = left;
            successor->balance = node->balance;

            if (left != NULL) {
                left->parent = successor;
            }
            if (node == t->root) {
                t->root = successor;
            } else {
                if (parent->left == node) {
                    parent->left = successor;
                } else {
                    parent->right = successor;
                }
            }
            Tree_DeleteBalance (t, successor, -1);
        } else {


...


void Tree_Replace (Node target, Node source) {
    Node left = source->left;
    Node right = source->right;

    target->balance = source->balance;
    target->data = source->data;
    target->left = left;
    target->right = right;

    if (left != NULL) {
        left->parent = target;
    }

    if (right != NULL) {
        right->parent = target;
    }
}