Company: MYI
Filing Date: 2025-08-08
Form Type: PRE 14A
Source: 0001193125-25-176952
Chunk: 350

Company: BLACKROCK MUNIYIELD QUALITY FUND III, INC.
Filing Date: 2025-08-08
Form: PRE 14A
Chunk 350
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 | Restricted Default. Indicates an entity that has defaulted on one or more of its financial commitments, although it        
 continues to meet other financial obligations. Typically applicable to entity ratings only.                                |
| D  |     | Default. Indicates a broad-based default event for an entity, or the default of a short-term obligation.                   |

D-8

| BlackRock MuniYield Quality Fund III, Inc. 
 PO Box 43131 Providence, RI                
 02940-3131                                 |     | EVERY VOTE IS IMPORTANT          |     |                            |
|                                            |     |                                  |     | MAIL                       |
|                                            |     |                                  |     | Vote, Sign and Mail in the |
|                                            |     | enclosed Business Reply Envelope |     |                            |

PREFERRED SHARES The undersigned hereby appoints John M. Perlowski and Jay M. Fife, and each of them, as proxies, each with the power to appoint his substitute, and hereby authorizes them to represent and to vote, as designated on the reverse side hereof, all of the shares of BlackRock MuniYield Quality Fund III, Inc., a Maryland corporation (the “Acquiring Fund”), that the undersigned is entitled to vote at the Joint Special Meeting of Shareholders of the Fund to be held on October 15, 2025, at [•] a.m. (Eastern Time) (the “Joint Special Meeting”), and any adjournment(s) or postponement(s) thereof, to cast on behalf of the undersigned all votes that the undersigned is entitled to cast at the Joint Special Meeting and otherwise to represent the undersigned at the Joint Special Meeting with all powers possessed by the undersigned as if personally present at the Joint Special Meeting. The Joint Special Meeting will be held in a virtual meeting format only, at the following Website: https://meetnow.global/MUUJ79Z. To attend and participate in the virtual Joint Special Meeting, enter the 14-digitcontrol number from the shaded box on this card. The validity of this proxy is governed by Maryland law. This proxy does not revoke any prior powers of attorney except for prior proxies given in connection with the Joint Special Meeting. The undersigned hereby acknowledges receipt of the Joint Proxy Statement/Prospectus, the terms of which are incorporated herein by reference, and revokes any proxy heretofore given with respect to the Joint Special Meeting. THIS PROXY, IF PROPERLY EXECUTED, WILL BE VOTED IN