[Goldar's Revenge]

Different circumstances. In Green With Evil Zordon was lost interdemensionally. They were complete cut off from communications. In Return of An Old Friend, Zordon was completely drained from powering Tommy. He didn't just recharge the coin. He basically let Tommy borrow all the energy he had. The Power Coins were able to restore him. This wouldn't have worked in the latter episode, since the problem wasn't powerloss. Its probably why Rita instructed Tommy to send Zordon to another dimension.