https://www.epo.org/en/service-support/faq/applying-patent/cnipa-epo-pilot-programme/epo-international-searching-4

Can I accelerate the grant proceedings by choosing the EPO as ISA?

Yes. Choosing the EPO as ISA dispenses with the need to carry out a European search upon entry into the European phase, which can save you up to 12 months in this phase. You can save even more time if you request early processing under Article 23(2) or Article 40(2) PCT and enter the European phase before the end of the maximum available period of 31 months from the priority date. You can also opt to waive your right to a communication under Rules 161 and 162 EPC and so reduce the duration of the proceedings in the European phase by a further six months.

Lastly, under the PCT Patent Prosecution Highway scheme (PPH), if your claims have been determined to be patentable/allowable by the EPO as ISA (and/or IPEA) you can have a corresponding application that has been filed with a PPH partner office processed in an accelerated manner. The PPH also allows the offices involved to exploit available work results. Where the EPO is ISA (and/or IPEA), you can use any PCT work products from the EPO to accelerate the processing of your application before the patent offices of Australia, Canada, P.R. China, Colombia, Israel, Japan, Republic of Korea, Malaysia, Mexico, Peru, the Philippines, Singapore and the USA.